Keep sub-task resets apart from tick copies, scope copy markers (#160)

CHANGELOG.md

@@ -7,6 +7,14 @@ All notable changes to this project are documented here. The format follows
 
 ## [Unreleased]
 
+### Fixed
+- Sub-tasks of a repeating task start over when ticking off its current
+  occurrence moves it on to its next date, as in tasks.org: completed and
+  half-done ones open again, and dated ones move along with the task. Before,
+  the next occurrence showed them already ticked. Unticking gives them back
+  their state and dates, and repeating sub-tasks keep their own schedule
+  (#160).
+
 ## [1.3.1] - 2026-11-09
 
 ### Changed

app/schemas/de.jeanlucmakiola.agendula.data.tasks.room.TasksDatabase/6.json

@@ -0,0 +1,775 @@
+{
+  "formatVersion": 1,
+  "database": {
+    "version": 6,
+    "identityHash": "6c8058a22084f0af602bc2f23c949b3c",
+    "entities": [
+      {
+        "tableName": "accounts",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`id` INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, `display_name` TEXT NOT NULL, `principal_url` TEXT, `home_set_url` TEXT, `username` TEXT, `last_sync_at` INTEGER, `last_sync_error` TEXT, `label` TEXT)",
+        "fields": [
+          {
+            "fieldPath": "id",
+            "columnName": "id",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "displayName",
+            "columnName": "display_name",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "principalUrl",
+            "columnName": "principal_url",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "homeSetUrl",
+            "columnName": "home_set_url",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "username",
+            "columnName": "username",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "lastSyncAt",
+            "columnName": "last_sync_at",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "lastSyncError",
+            "columnName": "last_sync_error",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "label",
+            "columnName": "label",
+            "affinity": "TEXT"
+          }
+        ],
+        "primaryKey": {
+          "autoGenerate": true,
+          "columnNames": [
+            "id"
+          ]
+        }
+      },
+      {
+        "tableName": "task_lists",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`id` INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, `name` TEXT NOT NULL, `color` INTEGER NOT NULL, `account_id` INTEGER, `is_visible` INTEGER NOT NULL DEFAULT 1, `is_synced` INTEGER NOT NULL DEFAULT 1, `owner` TEXT, `is_read_only` INTEGER NOT NULL DEFAULT 0, `sort_order` INTEGER NOT NULL DEFAULT 0, `href` TEXT, `ctag` TEXT, `sync_token` TEXT, `is_dirty` INTEGER NOT NULL DEFAULT 0, FOREIGN KEY(`account_id`) REFERENCES `accounts`(`id`) ON UPDATE NO ACTION ON DELETE SET NULL )",
+        "fields": [
+          {
+            "fieldPath": "id",
+            "columnName": "id",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "name",
+            "columnName": "name",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "color",
+            "columnName": "color",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "accountId",
+            "columnName": "account_id",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "isVisible",
+            "columnName": "is_visible",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "1"
+          },
+          {
+            "fieldPath": "isSynced",
+            "columnName": "is_synced",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "1"
+          },
+          {
+            "fieldPath": "owner",
+            "columnName": "owner",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "isReadOnly",
+            "columnName": "is_read_only",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "0"
+          },
+          {
+            "fieldPath": "sortOrder",
+            "columnName": "sort_order",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "0"
+          },
+          {
+            "fieldPath": "href",
+            "columnName": "href",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "ctag",
+            "columnName": "ctag",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "syncToken",
+            "columnName": "sync_token",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "isDirty",
+            "columnName": "is_dirty",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "0"
+          }
+        ],
+        "primaryKey": {
+          "autoGenerate": true,
+          "columnNames": [
+            "id"
+          ]
+        },
+        "indices": [
+          {
+            "name": "index_task_lists_account_id",
+            "unique": false,
+            "columnNames": [
+              "account_id"
+            ],
+            "orders": [],
+            "createSql": "CREATE INDEX IF NOT EXISTS `index_task_lists_account_id` ON `${TABLE_NAME}` (`account_id`)"
+          }
+        ],
+        "foreignKeys": [
+          {
+            "table": "accounts",
+            "onDelete": "SET NULL",
+            "onUpdate": "NO ACTION",
+            "columns": [
+              "account_id"
+            ],
+            "referencedColumns": [
+              "id"
+            ]
+          }
+        ]
+      },
+      {
+        "tableName": "tasks",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`id` INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, `list_id` INTEGER NOT NULL, `uid` TEXT NOT NULL, `href` TEXT, `etag` TEXT, `title` TEXT, `description` TEXT, `location` TEXT, `url` TEXT, `color` INTEGER, `categories` TEXT NOT NULL DEFAULT '', `status` INTEGER NOT NULL DEFAULT 0, `percent_complete` INTEGER, `completed_at` INTEGER, `priority` INTEGER NOT NULL DEFAULT 0, `classification` INTEGER, `dtstart` INTEGER, `due` INTEGER, `duration` TEXT, `is_all_day` INTEGER NOT NULL DEFAULT 0, `timezone` TEXT, `rrule` TEXT, `rdate` TEXT, `exdate` TEXT, `recurrence_id` INTEGER, `master_id` INTEGER, `parent_id` INTEGER, `sort_order` INTEGER NOT NULL DEFAULT 0, `created_at` INTEGER, `last_modified` INTEGER, `sequence` INTEGER NOT NULL DEFAULT 0, `is_dirty` INTEGER NOT NULL DEFAULT 0, `is_deleted` INTEGER NOT NULL DEFAULT 0, `unknown_properties` TEXT, `reminders_off` INTEGER NOT NULL DEFAULT 0, FOREIGN KEY(`list_id`) REFERENCES `task_lists`(`id`) ON UPDATE NO ACTION ON DELETE CASCADE , FOREIGN KEY(`master_id`) REFERENCES `tasks`(`id`) ON UPDATE NO ACTION ON DELETE CASCADE , FOREIGN KEY(`parent_id`) REFERENCES `tasks`(`id`) ON UPDATE NO ACTION ON DELETE SET NULL )",
+        "fields": [
+          {
+            "fieldPath": "id",
+            "columnName": "id",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "listId",
+            "columnName": "list_id",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "uid",
+            "columnName": "uid",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "href",
+            "columnName": "href",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "etag",
+            "columnName": "etag",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "title",
+            "columnName": "title",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "description",
+            "columnName": "description",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "location",
+            "columnName": "location",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "url",
+            "columnName": "url",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "color",
+            "columnName": "color",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "categories",
+            "columnName": "categories",
+            "affinity": "TEXT",
+            "notNull": true,
+            "defaultValue": "''"
+          },
+          {
+            "fieldPath": "status",
+            "columnName": "status",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "0"
+          },
+          {
+            "fieldPath": "percentComplete",
+            "columnName": "percent_complete",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "completedAt",
+            "columnName": "completed_at",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "priority",
+            "columnName": "priority",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "0"
+          },
+          {
+            "fieldPath": "classification",
+            "columnName": "classification",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "dtstart",
+            "columnName": "dtstart",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "due",
+            "columnName": "due",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "duration",
+            "columnName": "duration",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "isAllDay",
+            "columnName": "is_all_day",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "0"
+          },
+          {
+            "fieldPath": "timezone",
+            "columnName": "timezone",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "rrule",
+            "columnName": "rrule",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "rdate",
+            "columnName": "rdate",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "exdate",
+            "columnName": "exdate",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "recurrenceId",
+            "columnName": "recurrence_id",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "masterId",
+            "columnName": "master_id",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "parentId",
+            "columnName": "parent_id",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "sortOrder",
+            "columnName": "sort_order",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "0"
+          },
+          {
+            "fieldPath": "createdAt",
+            "columnName": "created_at",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "lastModified",
+            "columnName": "last_modified",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "sequence",
+            "columnName": "sequence",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "0"
+          },
+          {
+            "fieldPath": "isDirty",
+            "columnName": "is_dirty",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "0"
+          },
+          {
+            "fieldPath": "isDeleted",
+            "columnName": "is_deleted",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "0"
+          },
+          {
+            "fieldPath": "unknownProperties",
+            "columnName": "unknown_properties",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "remindersOff",
+            "columnName": "reminders_off",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "0"
+          }
+        ],
+        "primaryKey": {
+          "autoGenerate": true,
+          "columnNames": [
+            "id"
+          ]
+        },
+        "indices": [
+          {
+            "name": "index_tasks_list_id_is_deleted",
+            "unique": false,
+            "columnNames": [
+              "list_id",
+              "is_deleted"
+            ],
+            "orders": [],
+            "createSql": "CREATE INDEX IF NOT EXISTS `index_tasks_list_id_is_deleted` ON `${TABLE_NAME}` (`list_id`, `is_deleted`)"
+          },
+          {
+            "name": "index_tasks_parent_id",
+            "unique": false,
+            "columnNames": [
+              "parent_id"
+            ],
+            "orders": [],
+            "createSql": "CREATE INDEX IF NOT EXISTS `index_tasks_parent_id` ON `${TABLE_NAME}` (`parent_id`)"
+          },
+          {
+            "name": "index_tasks_master_id_recurrence_id",
+            "unique": false,
+            "columnNames": [
+              "master_id",
+              "recurrence_id"
+            ],
+            "orders": [],
+            "createSql": "CREATE INDEX IF NOT EXISTS `index_tasks_master_id_recurrence_id` ON `${TABLE_NAME}` (`master_id`, `recurrence_id`)"
+          },
+          {
+            "name": "index_tasks_is_dirty",
+            "unique": false,
+            "columnNames": [
+              "is_dirty"
+            ],
+            "orders": [],
+            "createSql": "CREATE INDEX IF NOT EXISTS `index_tasks_is_dirty` ON `${TABLE_NAME}` (`is_dirty`)"
+          },
+          {
+            "name": "index_tasks_list_id_uid_recurrence_id",
+            "unique": true,
+            "columnNames": [
+              "list_id",
+              "uid",
+              "recurrence_id"
+            ],
+            "orders": [],
+            "createSql": "CREATE UNIQUE INDEX IF NOT EXISTS `index_tasks_list_id_uid_recurrence_id` ON `${TABLE_NAME}` (`list_id`, `uid`, `recurrence_id`)"
+          }
+        ],
+        "foreignKeys": [
+          {
+            "table": "task_lists",
+            "onDelete": "CASCADE",
+            "onUpdate": "NO ACTION",
+            "columns": [
+              "list_id"
+            ],
+            "referencedColumns": [
+              "id"
+            ]
+          },
+          {
+            "table": "tasks",
+            "onDelete": "CASCADE",
+            "onUpdate": "NO ACTION",
+            "columns": [
+              "master_id"
+            ],
+            "referencedColumns": [
+              "id"
+            ]
+          },
+          {
+            "table": "tasks",
+            "onDelete": "SET NULL",
+            "onUpdate": "NO ACTION",
+            "columns": [
+              "parent_id"
+            ],
+            "referencedColumns": [
+              "id"
+            ]
+          }
+        ]
+      },
+      {
+        "tableName": "task_alarms",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`id` INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, `task_id` INTEGER NOT NULL, `minutes_before` INTEGER NOT NULL, `reference` TEXT NOT NULL DEFAULT 'DUE', `message` TEXT, `uid` TEXT NOT NULL DEFAULT '', `raw` TEXT, FOREIGN KEY(`task_id`) REFERENCES `tasks`(`id`) ON UPDATE NO ACTION ON DELETE CASCADE )",
+        "fields": [
+          {
+            "fieldPath": "id",
+            "columnName": "id",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "taskId",
+            "columnName": "task_id",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "minutesBefore",
+            "columnName": "minutes_before",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "reference",
+            "columnName": "reference",
+            "affinity": "TEXT",
+            "notNull": true,
+            "defaultValue": "'DUE'"
+          },
+          {
+            "fieldPath": "message",
+            "columnName": "message",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "uid",
+            "columnName": "uid",
+            "affinity": "TEXT",
+            "notNull": true,
+            "defaultValue": "''"
+          },
+          {
+            "fieldPath": "raw",
+            "columnName": "raw",
+            "affinity": "TEXT"
+          }
+        ],
+        "primaryKey": {
+          "autoGenerate": true,
+          "columnNames": [
+            "id"
+          ]
+        },
+        "indices": [
+          {
+            "name": "index_task_alarms_task_id",
+            "unique": false,
+            "columnNames": [
+              "task_id"
+            ],
+            "orders": [],
+            "createSql": "CREATE INDEX IF NOT EXISTS `index_task_alarms_task_id` ON `${TABLE_NAME}` (`task_id`)"
+          }
+        ],
+        "foreignKeys": [
+          {
+            "table": "tasks",
+            "onDelete": "CASCADE",
+            "onUpdate": "NO ACTION",
+            "columns": [
+              "task_id"
+            ],
+            "referencedColumns": [
+              "id"
+            ]
+          }
+        ]
+      },
+      {
+        "tableName": "advanced_occurrences",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`copy_id` INTEGER NOT NULL, `master_id` INTEGER NOT NULL, `anchor` INTEGER NOT NULL, `advanced_to` INTEGER NOT NULL, `prior_dtstart` INTEGER, `prior_due` INTEGER, `prior_status` INTEGER NOT NULL, `prior_percent_complete` INTEGER, `prior_completed_at` INTEGER, `spent` INTEGER NOT NULL, `rule_after` TEXT, `dropped_exdates` TEXT NOT NULL DEFAULT '', `from_override` INTEGER NOT NULL, `undoable` INTEGER NOT NULL DEFAULT 1, `settled` INTEGER NOT NULL DEFAULT 0, `reset_subtasks` TEXT NOT NULL DEFAULT '', PRIMARY KEY(`copy_id`), FOREIGN KEY(`copy_id`) REFERENCES `tasks`(`id`) ON UPDATE NO ACTION ON DELETE CASCADE , FOREIGN KEY(`master_id`) REFERENCES `tasks`(`id`) ON UPDATE NO ACTION ON DELETE CASCADE )",
+        "fields": [
+          {
+            "fieldPath": "copyId",
+            "columnName": "copy_id",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "masterId",
+            "columnName": "master_id",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "anchor",
+            "columnName": "anchor",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "advancedTo",
+            "columnName": "advanced_to",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "priorDtstart",
+            "columnName": "prior_dtstart",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "priorDue",
+            "columnName": "prior_due",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "priorStatus",
+            "columnName": "prior_status",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "priorPercentComplete",
+            "columnName": "prior_percent_complete",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "priorCompletedAt",
+            "columnName": "prior_completed_at",
+            "affinity": "INTEGER"
+          },
+          {
+            "fieldPath": "spent",
+            "columnName": "spent",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "ruleAfter",
+            "columnName": "rule_after",
+            "affinity": "TEXT"
+          },
+          {
+            "fieldPath": "droppedExdates",
+            "columnName": "dropped_exdates",
+            "affinity": "TEXT",
+            "notNull": true,
+            "defaultValue": "''"
+          },
+          {
+            "fieldPath": "fromOverride",
+            "columnName": "from_override",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "undoable",
+            "columnName": "undoable",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "1"
+          },
+          {
+            "fieldPath": "settled",
+            "columnName": "settled",
+            "affinity": "INTEGER",
+            "notNull": true,
+            "defaultValue": "0"
+          },
+          {
+            "fieldPath": "resetSubtasks",
+            "columnName": "reset_subtasks",
+            "affinity": "TEXT",
+            "notNull": true,
+            "defaultValue": "''"
+          }
+        ],
+        "primaryKey": {
+          "autoGenerate": false,
+          "columnNames": [
+            "copy_id"
+          ]
+        },
+        "indices": [
+          {
+            "name": "index_advanced_occurrences_master_id_anchor",
+            "unique": false,
+            "columnNames": [
+              "master_id",
+              "anchor"
+            ],
+            "orders": [],
+            "createSql": "CREATE INDEX IF NOT EXISTS `index_advanced_occurrences_master_id_anchor` ON `${TABLE_NAME}` (`master_id`, `anchor`)"
+          }
+        ],
+        "foreignKeys": [
+          {
+            "table": "tasks",
+            "onDelete": "CASCADE",
+            "onUpdate": "NO ACTION",
+            "columns": [
+              "copy_id"
+            ],
+            "referencedColumns": [
+              "id"
+            ]
+          },
+          {
+            "table": "tasks",
+            "onDelete": "CASCADE",
+            "onUpdate": "NO ACTION",
+            "columns": [
+              "master_id"
+            ],
+            "referencedColumns": [
+              "id"
+            ]
+          }
+        ]
+      },
+      {
+        "tableName": "advanced_detached",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`id` INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, `copy_id` INTEGER NOT NULL, `anchor` INTEGER NOT NULL, `task_id` INTEGER, FOREIGN KEY(`copy_id`) REFERENCES `advanced_occurrences`(`copy_id`) ON UPDATE NO ACTION ON DELETE CASCADE , FOREIGN KEY(`task_id`) REFERENCES `tasks`(`id`) ON UPDATE NO ACTION ON DELETE SET NULL )",
+        "fields": [
+          {
+            "fieldPath": "id",
+            "columnName": "id",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "copyId",
+            "columnName": "copy_id",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "anchor",
+            "columnName": "anchor",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "taskId",
+            "columnName": "task_id",
+            "affinity": "INTEGER"
+          }
+        ],
+        "primaryKey": {
+          "autoGenerate": true,
+          "columnNames": [
+            "id"
+          ]
+        },
+        "indices": [
+          {
+            "name": "index_advanced_detached_copy_id",
+            "unique": false,
+            "columnNames": [
+              "copy_id"
+            ],
+            "orders": [],
+            "createSql": "CREATE INDEX IF NOT EXISTS `index_advanced_detached_copy_id` ON `${TABLE_NAME}` (`copy_id`)"
+          },
+          {
+            "name": "index_advanced_detached_task_id",
+            "unique": false,
+            "columnNames": [
+              "task_id"
+            ],
+            "orders": [],
+            "createSql": "CREATE INDEX IF NOT EXISTS `index_advanced_detached_task_id` ON `${TABLE_NAME}` (`task_id`)"
+          }
+        ],
+        "foreignKeys": [
+          {
+            "table": "advanced_occurrences",
+            "onDelete": "CASCADE",
+            "onUpdate": "NO ACTION",
+            "columns": [
+              "copy_id"
+            ],
+            "referencedColumns": [
+              "copy_id"
+            ]
+          },
+          {
+            "table": "tasks",
+            "onDelete": "SET NULL",
+            "onUpdate": "NO ACTION",
+            "columns": [
+              "task_id"
+            ],
+            "referencedColumns": [
+              "id"
+            ]
+          }
+        ]
+      }
+    ],
+    "setupQueries": [
+      "CREATE TABLE IF NOT EXISTS room_master_table (id INTEGER PRIMARY KEY,identity_hash TEXT)",
+      "INSERT OR REPLACE INTO room_master_table (id,identity_hash) VALUES(42, '6c8058a22084f0af602bc2f23c949b3c')"
+    ]
+  }
+}

app/src/androidTest/java/de/jeanlucmakiola/agendula/data/tasks/room/RoomTasksDataSourceTest.kt

@@ -14,6 +14,7 @@ import org.junit.Test
 import org.junit.runner.RunWith
 import kotlin.time.Clock
 import kotlin.time.Duration.Companion.days
+import kotlin.time.Duration.Companion.hours
 import kotlin.time.Instant
 
 /**
@@ -700,6 +701,144 @@ class RoomTasksDataSourceTest {
         assertThat(db.tasks().overrides(id)).hasSize(1)
     }
 
+    @Test
+    fun movingARoutineOnReopensItsCompletedSubtasks() {
+        val at = now
+        val id = source.insertTask(form(title = "Routine"))
+        makeRecurring(id, at)
+        val done = source.insertTask(form(title = "Step").copy(parentId = id))
+        val nested = source.insertTask(form(title = "Nested").copy(parentId = done))
+        val cancelled = source.insertTask(form(title = "Skipped").copy(parentId = id))
+        val daily = source.insertTask(form(title = "Daily part").copy(parentId = id))
+        makeRecurring(daily, at, rule = "FREQ=DAILY")
+        source.setCompleted(done, completed = true)
+        source.setCompleted(nested, completed = true)
+        source.setCancelled(cancelled, cancelled = true)
+        source.setCompletedInstance(daily, at, completed = true)
+
+        source.setCompletedInstance(id, at, completed = true)
+
+        assertThat(db.tasks().entity(id)!!.dtstart).isEqualTo(at + 7.days)
+        assertThat(db.tasks().entity(done)!!.status).isEqualTo(TaskStatus.NEEDS_ACTION)
+        assertThat(db.tasks().entity(done)!!.completedAt).isNull()
+        assertThat(db.tasks().entity(nested)!!.status).isEqualTo(TaskStatus.NEEDS_ACTION)
+        assertThat(db.tasks().entity(cancelled)!!.status).isEqualTo(TaskStatus.CANCELLED)
+        // A recurring subtask has its own series, and its closed occurrence stays closed.
+        assertThat(db.tasks().overrides(daily).single().status).isEqualTo(TaskStatus.COMPLETED)
+    }
+
+    @Test
+    fun aHalfDoneSubtaskStartsOverToo() {
+        val at = now
+        val id = source.insertTask(form(title = "Routine"))
+        makeRecurring(id, at)
+        val step = source.insertTask(form(title = "Step", percentComplete = 40).copy(parentId = id))
+        db.tasks().update(db.tasks().entity(step)!!.copy(status = TaskStatus.IN_PROCESS, percentComplete = 40))
+
+        source.setCompletedInstance(id, at, completed = true)
+
+        assertThat(db.tasks().entity(step)!!.status).isEqualTo(TaskStatus.NEEDS_ACTION)
+        assertThat(db.tasks().entity(step)!!.percentComplete).isNull()
+    }
+
+    @Test
+    fun movingARoutineBackRestoresTheSubtasksItReset() {
+        val at = now
+        val id = source.insertTask(form(title = "Routine"))
+        makeRecurring(id, at)
+        val done = source.insertTask(form(title = "Step").copy(parentId = id))
+        val touched = source.insertTask(form(title = "Touched since").copy(parentId = id))
+        source.setCompleted(done, completed = true)
+        source.setCompleted(touched, completed = true)
+        val completedAt = db.tasks().entity(done)!!.completedAt
+        source.setCompletedInstance(id, at, completed = true)
+        db.tasks().update(db.tasks().entity(touched)!!.copy(percentComplete = 30))
+
+        source.setCompletedInstance(id, at, completed = false)
+
+        assertThat(db.tasks().entity(id)!!.dtstart).isEqualTo(at)
+        assertThat(db.tasks().entity(done)!!.status).isEqualTo(TaskStatus.COMPLETED)
+        assertThat(db.tasks().entity(done)!!.completedAt).isEqualTo(completedAt)
+        // Changed after the reset: the user's state wins.
+        assertThat(db.tasks().entity(touched)!!.status).isEqualTo(TaskStatus.NEEDS_ACTION)
+        assertThat(db.tasks().entity(touched)!!.percentComplete).isEqualTo(30)
+    }
+
+    @Test
+    fun aDatedSubtaskMovesWithItsRoutineAndBack() {
+        val at = now
+        val id = source.insertTask(form(title = "Routine"))
+        makeRecurring(id, at)
+        val step = source.insertTask(form(title = "Step", due = at + 1.days).copy(parentId = id))
+        val undated = source.insertTask(form(title = "Undated").copy(parentId = id))
+        source.setCompleted(step, completed = true)
+        val due = db.tasks().entity(step)!!.due!!
+
+        source.setCompletedInstance(id, at, completed = true)
+
+        // A week of wall-clock time: an hour either way across a DST change.
+        assertThat(db.tasks().entity(step)!!.due!! - due).isIn(com.google.common.collect.Range.closed(7.days - 1.hours, 7.days + 1.hours))
+        assertThat(db.tasks().entity(step)!!.status).isEqualTo(TaskStatus.NEEDS_ACTION)
+        assertThat(db.tasks().entity(undated)!!.due).isNull()
+
+        source.setCompletedInstance(id, at, completed = false)
+
+        assertThat(db.tasks().entity(step)!!.due).isEqualTo(due)
+        assertThat(db.tasks().entity(step)!!.status).isEqualTo(TaskStatus.COMPLETED)
+    }
+
+    @Test
+    fun aMarkedCopyUnderARoutineIsLeftAlone() {
+        val at = now
+        val id = source.insertTask(form(title = "Routine"))
+        makeRecurring(id, at)
+        val routineUid = db.tasks().entity(id)!!.uid
+        val copy = source.insertTask(form(title = "Daily part").copy(parentId = id))
+        val elsewhere = source.insertTask(form(title = "Moved here").copy(parentId = id))
+        source.setCompleted(copy, completed = true)
+        source.setCompleted(elsewhere, completed = true)
+        db.tasks().update(db.tasks().entity(copy)!!.copy(unknownProperties = "X-AGENDULA-TICK-COPY:$routineUid"))
+        db.tasks().update(db.tasks().entity(elsewhere)!!.copy(unknownProperties = "X-AGENDULA-TICK-COPY:another-parent"))
+
+        source.setCompletedInstance(id, at, completed = true)
+
+        assertThat(db.tasks().entity(copy)!!.status).isEqualTo(TaskStatus.COMPLETED)
+        // Its marker names a parent it no longer sits under: an ordinary sub-task here.
+        assertThat(db.tasks().entity(elsewhere)!!.status).isEqualTo(TaskStatus.NEEDS_ACTION)
+    }
+
+    @Test
+    fun aLegacyResetRecordRestoresTheStateAndLeavesTheDates() {
+        val at = now
+        val id = source.insertTask(form(title = "Routine"))
+        makeRecurring(id, at)
+        val step = source.insertTask(form(title = "Step", due = at + 1.days).copy(parentId = id))
+        source.setCompleted(step, completed = true)
+        source.setCompletedInstance(id, at, completed = true)
+        val record = db.advancedOccurrences().forMaster(id).single()
+        db.advancedOccurrences().insert(record.copy(resetSubtasks = "$step,COMPLETED,100,"))
+        val movedDue = db.tasks().entity(step)!!.due
+
+        source.setCompletedInstance(id, at, completed = false)
+
+        assertThat(db.tasks().entity(step)!!.status).isEqualTo(TaskStatus.COMPLETED)
+        assertThat(db.tasks().entity(step)!!.due).isEqualTo(movedDue)
+    }
+
+    @Test
+    fun aRoutineTickedOnItsLastOccurrenceLeavesItsSubtasksDone() {
+        val at = now
+        val id = source.insertTask(form(title = "Once more"))
+        makeRecurring(id, at, rule = "FREQ=WEEKLY;COUNT=1")
+        val step = source.insertTask(form(title = "Step").copy(parentId = id))
+        source.setCompleted(step, completed = true)
+
+        source.setCompletedInstance(id, at, completed = true)
+
+        assertThat(db.tasks().entity(id)!!.status).isEqualTo(TaskStatus.COMPLETED)
+        assertThat(db.tasks().entity(step)!!.status).isEqualTo(TaskStatus.COMPLETED)
+    }
+
     @Test
     fun aSeriesReshapedSinceIsNotMovedBack() {
         val at = now

app/src/androidTest/java/de/jeanlucmakiola/agendula/data/tasks/room/TasksDatabaseMigrationTest.kt

@@ -174,6 +174,25 @@ class TasksDatabaseMigrationTest {
         }
     }
 
+    @Test
+    fun addsAnEmptyResetSubtasksRecord() {
+        helper.createDatabase(TEST_DB, 5).use { db ->
+            db.execSQL("INSERT INTO task_lists (id, name, color) VALUES (1, 'Personal', 0)")
+            db.execSQL("INSERT INTO tasks (id, list_id, uid) VALUES (1, 1, 'a'), (2, 1, 'b')")
+            db.execSQL(
+                "INSERT INTO advanced_occurrences (copy_id, master_id, anchor, advanced_to, prior_status, spent, from_override) " +
+                    "VALUES (2, 1, 0, 1, 0, 1, 0)",
+            )
+        }
+
+        helper.runMigrationsAndValidate(TEST_DB, 6, true, TasksDatabase.MIGRATION_5_6).use { db ->
+            db.query("SELECT reset_subtasks FROM advanced_occurrences").use { c ->
+                assertThat(c.moveToFirst()).isTrue()
+                assertThat(c.getString(0)).isEmpty()
+            }
+        }
+    }
+
     private companion object {
         const val TEST_DB = "migration-test.db"
     }

app/src/main/java/de/jeanlucmakiola/agendula/data/di/DataModule.kt

@@ -89,7 +89,7 @@ object DataProvideModule {
             // backed-up `.db` does not. The backup rules carry all three files and
             // the app checkpoints on ON_STOP.
             .setJournalMode(RoomDatabase.JournalMode.WRITE_AHEAD_LOGGING)
-            .addMigrations(TasksDatabase.MIGRATION_1_2, TasksDatabase.MIGRATION_2_3, TasksDatabase.MIGRATION_3_4, TasksDatabase.MIGRATION_4_5)
+            .addMigrations(TasksDatabase.MIGRATION_1_2, TasksDatabase.MIGRATION_2_3, TasksDatabase.MIGRATION_3_4, TasksDatabase.MIGRATION_4_5, TasksDatabase.MIGRATION_5_6)
             .build()
 
     /**

app/src/main/java/de/jeanlucmakiola/agendula/data/tasks/AndroidTasksDataSource.kt

@@ -25,6 +25,8 @@ import de.jeanlucmakiola.agendula.domain.TaskForm
 import de.jeanlucmakiola.agendula.domain.TaskList
 import de.jeanlucmakiola.agendula.domain.export.ExportTask
 import de.jeanlucmakiola.agendula.domain.normalizeTags
+import de.jeanlucmakiola.agendula.domain.statusFromInt
+import de.jeanlucmakiola.agendula.domain.toInt
 import de.jeanlucmakiola.agendula.domain.recurrence.ExpansionWindow
 import de.jeanlucmakiola.agendula.domain.recurrence.RecurrenceExpander
 import de.jeanlucmakiola.agendula.domain.recurrence.RecurrenceSpec
@@ -135,21 +137,8 @@ class AndroidTasksDataSource @Inject constructor(
      * the window still counts. All columns and a lenient `_deleted`, as in
      * [exportTasks], since the table's shape varies across providers.
      */
-    override fun subtaskIds(parentTaskId: Long): List<Long> = resolver.query(
-        TasksContract.tasksUri(authority()),
-        null,
-        "${Tasks.PARENT_ID} = ? AND (${Tasks.DELETED} IS NULL OR ${Tasks.DELETED} = 0)",
-        arrayOf(parentTaskId.toString()),
-        null,
-    )?.use { c ->
-        val r = CursorColumnReader(c)
-        buildList {
-            while (c.moveToNext()) {
-                if (r.getLong(Tasks.ORIGINAL_INSTANCE_ID) != null) continue
-                r.getLong(Tasks.ID)?.takeIf { it != parentTaskId }?.let(::add)
-            }
-        }
-    } ?: emptyList()
+    override fun subtaskIds(parentTaskId: Long): List<Long> =
+        childRows(authority(), parentTaskId, projection = null) { it.getLong(Tasks.ID) }
 
     /**
      * All columns and no sort: the instances view differs across provider
@@ -207,12 +196,7 @@ class AndroidTasksDataSource @Inject constructor(
         filterArgs: List<String> = emptyList(),
         sortOrder: String? = null,
         read: (ColumnReader) -> T?,
-    ): List<T> = ids.distinct().chunked(MAX_SQL_ARGS - filterArgs.size).flatMap { chunk ->
-        val selection = buildString {
-            append("$idColumn IN (${chunk.joinToString(",") { "?" }})")
-            if (filter != null) append(" AND ($filter)")
-        }
-        val args = (chunk.map(Long::toString) + filterArgs).toTypedArray()
+    ): List<T> = inSelections(idColumn, ids, filter, filterArgs).flatMap { (selection, args) ->
         resolver.query(uri, projection, selection, args, sortOrder)?.use { c ->
             val reader = CursorColumnReader(c)
             buildList { while (c.moveToNext()) read(reader)?.let(::add) }
@@ -345,18 +329,7 @@ class AndroidTasksDataSource @Inject constructor(
         arrayOf(Tasks.RRULE, Tasks.RDATE, Tasks.EXDATE, Tasks.DTSTART, Tasks.DUE, Tasks.IS_ALLDAY, Tasks.TZ),
         null, null, null,
     )?.use { c ->
-        if (!c.moveToFirst()) return@use null
-        val r = CursorColumnReader(c)
-        val anchor = r.getLong(Tasks.DTSTART) ?: r.getLong(Tasks.DUE) ?: return@use null
-        val rule = TaskMapper.seriesRule(r)
-        RecurrenceSpec(
-            rrule = rule?.rrule,
-            rdate = rule?.rdate,
-            exdate = r.getString(Tasks.EXDATE),
-            anchor = Instant.fromEpochMilliseconds(anchor),
-            isAllDay = r.getBoolean(Tasks.IS_ALLDAY),
-            timeZone = r.getString(Tasks.TZ),
-        )
+        if (c.moveToFirst()) TaskMapper.seriesSpec(CursorColumnReader(c)) else null
     }
 
     /** End the master's rule before [occurrenceStart], and drop the exceptions past it. */
@@ -753,6 +726,8 @@ class AndroidTasksDataSource @Inject constructor(
      * Runs [write], and when it closed an occurrence the provider then detached
      * into a task of its own, remembers that copy, so the occurrence can still be
      * read and reopened, and how the series moved, so reopening can move it back.
+     * When the series moved on, its sub-tasks start over for the next occurrence,
+     * and [resets] remembers how they were (#160), with or without a copy.
      */
     private fun rememberingCopy(taskId: Long, occurrenceStart: Instant, closing: Boolean, write: () -> Int): Int {
         if (!closing) return write()
@@ -761,9 +736,18 @@ class AndroidTasksDataSource @Inject constructor(
         val before = runCatching { seriesState(authority, taskId) }.getOrNull()
         return write().also { rows ->
             if (rows > 0) {
+                val after = before?.let {
+                    runCatching { seriesState(authority, taskId) }
+                        .onFailure { Log.w(TAG, "Reading the series after the tick failed", it) }
+                        .getOrNull()?.takeIf { it != before }
+                }
+                if (before != null && after != null && SubtaskReset.movedOn(before, after)) {
+                    runCatching { resetSubtasks(authority, taskId, before, after) }
+                        .onFailure { Log.w(TAG, "Resetting the sub-tasks failed", it) }
+                }
                 runCatching {
                     detachedSince(authority, lastId)?.let { copy ->
-                        val after = before?.let { seriesState(authority, taskId) }?.takeIf { it != before }
+                        markCopy(authority, copy, taskId)
                         val tick = Tick(copy, taskId.takeIf { after != null }, before.takeIf { after != null }, after, System.currentTimeMillis())
                         ticks.put(ticks.key(authority, taskId, occurrenceStart), tick)
                     }
@@ -772,12 +756,143 @@ class AndroidTasksDataSource @Inject constructor(
         }
     }
 
+    /**
+     * Marks [copyId], left by ticking the recurring sub-task [seriesId], with the
+     * UID of the parent it sits under, where DAVx5 keeps and uploads unknown
+     * properties, so other installs know it too. A top-level series' copy sits
+     * under nothing a reset walks, so it is left unmarked.
+     */
+    private fun markCopy(authority: String, copyId: Long, seriesId: Long) {
+        runCatching {
+            val parentId = resolver.query(taskUri(authority, seriesId), arrayOf(Tasks.PARENT_ID), null, null, null)
+                ?.use { c -> if (c.moveToFirst() && !c.isNull(0)) c.getLong(0) else null } ?: return
+            val parentUid = uidOf(authority, parentId) ?: return
+            val values = mapOf(
+                Properties.TASK_ID to copyId,
+                Properties.MIMETYPE to SubtaskReset.UNKNOWN_PROPERTY_MIMETYPE,
+                Properties.DATA0 to SubtaskReset.copyMarkerJson(parentUid),
+            )
+            resolver.insert(TasksContract.propertiesUri(authority), values.toContentValues())
+        }.onFailure { Log.w(TAG, "Marking the ticked copy failed", it) }
+    }
+
+    private fun uidOf(authority: String, taskId: Long): String? =
+        resolver.query(taskUri(authority, taskId), arrayOf(Tasks.UID), null, null, null)
+            ?.use { c -> if (c.moveToFirst()) c.getString(0) else null }
+
+    /** The parent UID each of [taskIds] carries a copy marker for. */
+    private fun markerParents(authority: String, taskIds: List<Long>): Map<Long, String> = runCatching {
+        queryByIds(
+            TasksContract.propertiesUri(authority),
+            arrayOf(Properties.TASK_ID, Properties.DATA0),
+            Properties.TASK_ID,
+            taskIds,
+            filter = "${Properties.MIMETYPE} = ?",
+            filterArgs = listOf(SubtaskReset.UNKNOWN_PROPERTY_MIMETYPE),
+        ) { r ->
+            val id = r.getLong(Properties.TASK_ID) ?: return@queryByIds null
+            SubtaskReset.markerParentFromJson(r.getString(Properties.DATA0))?.let { id to it }
+        }.toMap()
+    }.onFailure { Log.w(TAG, "Reading the copy markers failed", it) }.getOrDefault(emptyMap())
+
+    /**
+     * Resets what [SubtaskReset] picks under the series [seriesId], dated ones
+     * moved as the series moved from [before] to [after], and records it in
+     * [resets] first, under the anchor the series moved to.
+     */
+    private fun resetSubtasks(authority: String, seriesId: Long, before: Map<String, Any?>, after: Map<String, Any?>) {
+        val copies = ticks.copies(authority)
+        val uids = HashMap<Long, String?>().apply { put(seriesId, uidOf(authority, seriesId)) }
+        val reset = SubtaskReset.toReset(seriesId, SubtaskReset.shiftOf(before, after)) { id ->
+            val rows = childRows(authority, id, SUBTASK_STATE) { r ->
+                r.getLong(Tasks.ID)?.let { rowId ->
+                    uids[rowId] = r.getString(Tasks.UID)
+                    // Read now: the cursor is closed by the time the markers are in.
+                    val rrule = r.getString(Tasks.RRULE)
+                    val rdate = r.getString(Tasks.RDATE)
+                    val state = subtaskState(r)
+                    val dates = SubtaskDates(r.getLong(Tasks.DTSTART), r.getLong(Tasks.DUE))
+                    val allDay = r.getBoolean(Tasks.IS_ALLDAY)
+                    val tz = r.getString(Tasks.TZ)
+                    rowId to { markerParent: String? ->
+                        SubtaskReset.providerNode(
+                            rowId, rrule, rdate, copies, markerParent = markerParent, parentUid = uids[id],
+                            state = state, dates = dates, isAllDay = allDay, timeZone = tz,
+                        )
+                    }
+                }
+            }
+            val markers = markerParents(authority, rows.map { it.first })
+            rows.map { (rowId, node) -> node(markers[rowId]) }
+        }
+        if (reset.isEmpty()) return
+        SubtaskReset.anchor(after)?.let { resets.put(authority, seriesId, it, SubtaskReset.encode(reset), System.currentTimeMillis()) }
+        val ops = reset.map { subtaskOp(authority, it.id, SubtaskState.FRESH, it.dates?.takeIf { d -> d != it.priorDates }) }
+        resolver.applyBatch(authority, ArrayList(ops))
+    }
+
+    private fun subtaskState(r: ColumnReader) =
+        SubtaskState(statusFromInt(r.getInt(Tasks.STATUS)), r.getInt(Tasks.PERCENT_COMPLETE), r.getLong(Tasks.COMPLETED))
+
+    /** [state] onto sub-task [id], and [dates] when they change. */
+    private fun subtaskOp(authority: String, id: Long, state: SubtaskState, dates: SubtaskDates?): ContentProviderOperation {
+        val values = buildMap<String, Any?> {
+            put(Tasks.STATUS, state.status.toInt())
+            put(Tasks.PERCENT_COMPLETE, state.percent)
+            put(Tasks.COMPLETED, state.completedAt)
+            if (dates != null) {
+                put(Tasks.DTSTART, dates.start)
+                put(Tasks.DUE, dates.due)
+            }
+        }
+        return ContentProviderOperation.newUpdate(taskUri(authority, id)).withValues(values.toContentValues()).build()
+    }
+
+    /** The reset sub-tasks of [reset] that [SubtaskReset.toRestore] gives back their state and dates. */
+    private fun subtaskRestore(authority: String, reset: String?): List<ContentProviderOperation> {
+        val entries = SubtaskReset.decode(reset)
+        if (entries.isEmpty()) return emptyList()
+        val current = queryByIds(
+            TasksContract.tasksUri(authority),
+            SUBTASK_STATE,
+            Tasks.ID,
+            entries.map { it.id },
+            filter = "${Tasks.DELETED} IS NULL OR ${Tasks.DELETED} = 0",
+        ) { r ->
+            r.getLong(Tasks.ID)?.let {
+                it to SubtaskNow(subtaskState(r), SubtaskDates(r.getLong(Tasks.DTSTART), r.getLong(Tasks.DUE)), r.getBoolean(Tasks.IS_ALLDAY))
+            }
+        }.toMap()
+        val outcome = SubtaskReset.toRestore(entries, current::get)
+        if (outcome.changed.isNotEmpty()) Log.i(TAG, "Sub-tasks ${outcome.changed} changed since the reset and keep their state")
+        return outcome.restore.map { subtaskOp(authority, it.id, it.prior, it.priorDates?.takeIf { d -> d != it.dates }) }
+    }
+
+    /** Walks [parentId]'s direct sub-task rows, overrides left out, with [read] on each. */
+    private fun <T : Any> childRows(authority: String, parentId: Long, projection: Array<String>?, read: (ColumnReader) -> T?): List<T> =
+        resolver.query(
+            TasksContract.tasksUri(authority),
+            projection,
+            "${Tasks.PARENT_ID} = ? AND (${Tasks.DELETED} IS NULL OR ${Tasks.DELETED} = 0)",
+            arrayOf(parentId.toString()),
+            null,
+        )?.use { c ->
+            val r = CursorColumnReader(c)
+            buildList {
+                while (c.moveToNext()) {
+                    if (r.getLong(Tasks.ORIGINAL_INSTANCE_ID) != null || r.getLong(Tasks.ID) == parentId) continue
+                    read(r)?.let(::add)
+                }
+            }
+        } ?: emptyList()
+
     /**
      * Undoes the tick that left [taskId]'s occurrence at [occurrenceStart] — or,
      * with no occurrence, the tick that left the copy [taskId]: the series goes
      * back where it was and the copy goes, as long as the series is still where
-     * the tick moved it and the copy has nothing filed under it. False when it
-     * cannot, so the caller reopens the copy as a task of its own.
+     * the tick moved it and the copy has nothing filed under it. The sub-tasks
+     * the tick reset get their state back from [resets]. False when it cannot,
+     * so the caller reopens the copy as a task of its own.
      */
     private fun movedBack(taskId: Long, occurrenceStart: Instant?): Boolean = runCatching {
         val authority = authority()
@@ -786,21 +901,29 @@ class AndroidTasksDataSource @Inject constructor(
             ?: return false
         val series = tick.seriesId ?: return false
         val before = tick.before ?: return false
-        if (seriesState(authority, series) != tick.after || subtaskIds(tick.copyId).isNotEmpty()) return false
-        val restore = before.filter { (column, value) -> tick.after?.get(column) != value }
+        val after = tick.after ?: return false
+        // Compared on what the tick recorded: one from before IS_ALLDAY and TZ were read has neither.
+        val now = seriesState(authority, series) ?: return false
+        if (after.any { (column, value) -> now[column] != value } || subtaskIds(tick.copyId).isNotEmpty()) return false
+        val restore = before.filter { (column, value) -> after[column] != value }
         val ops = arrayListOf(
             ContentProviderOperation.newUpdate(taskUri(authority, series)).withValues(restore.toContentValues()).build(),
             ContentProviderOperation.newDelete(taskUri(authority, tick.copyId)).build(),
         )
+        val anchor = SubtaskReset.anchor(after)
+        anchor?.let { at ->
+            runCatching { ops += subtaskRestore(authority, resets.get(authority, series, at)) }
+                .onFailure { Log.w(TAG, "Reading the reset sub-tasks failed", it) }
+        }
         resolver.applyBatch(authority, ops)
         ticks.remove(key)
+        anchor?.let { resets.remove(authority, series, it) }
         true
     }.onFailure { Log.w(TAG, "Moving the series back failed", it) }.getOrDefault(false)
 
     /** The columns a tick moves a series by, or null when [taskId] is no series. */
-    private fun seriesState(authority: String, taskId: Long): Map<String, Any?>? {
-        if (seriesRules(listOf(taskId)).isEmpty()) return null
-        return resolver.query(taskUri(authority, taskId), SERIES_STATE, null, null, null)?.use { c ->
+    private fun seriesState(authority: String, taskId: Long): Map<String, Any?>? =
+        resolver.query(taskUri(authority, taskId), SERIES_STATE, null, null, null)?.use { c ->
             if (!c.moveToFirst()) return@use null
             SERIES_STATE.indices.associate { i ->
                 SERIES_STATE[i] to when (c.getType(i)) {
@@ -809,8 +932,7 @@ class AndroidTasksDataSource @Inject constructor(
                     else -> c.getString(i)
                 }
             }
-        }
-    }
+        }?.takeIf { state -> listOf(Tasks.RRULE, Tasks.RDATE).any { !(state[it] as? String).isNullOrBlank() } }
 
     private fun lastTaskId(authority: String): Long =
         resolver.query(TasksContract.tasksUri(authority), arrayOf(Tasks.ID), null, null, "${Tasks.ID} DESC")
@@ -830,7 +952,12 @@ class AndroidTasksDataSource @Inject constructor(
                 }
             }?.singleOrNull()
 
-    private val ticks = TickedCopies { context.getSharedPreferences(TICKED_COPIES, Context.MODE_PRIVATE) }
+    private val ticks = TickedCopies(
+        prefs = { context.getSharedPreferences(TICKED_COPIES, Context.MODE_PRIVATE) },
+        known = { context.getSharedPreferences(KNOWN_COPIES, Context.MODE_PRIVATE) },
+    )
+
+    private val resets = TickResets { context.getSharedPreferences(TICK_RESETS, Context.MODE_PRIVATE) }
 
     /** The copy a tick left for [taskId]'s occurrence at [occurrenceStart], if one was remembered. */
     private fun tickedCopy(taskId: Long, occurrenceStart: Instant): Long? =
@@ -939,10 +1066,22 @@ private const val MIGRATIONS = "provider_migrations"
 
 private const val TICKED_COPIES = "provider_ticked_copies"
 
-/** What a tick changes on a series, and an undo changes back. */
+/** Every copy a tick on this install left, kept past [TickedCopies.HORIZON_MS] alongside the marker on the row. */
+private const val KNOWN_COPIES = "provider_known_copies"
+
+/** The sub-tasks each tick reset, kept apart from its copy. */
+private const val TICK_RESETS = "provider_tick_resets"
+
+/** What resetting a sub-task reads: whether it recurs, its progress and its dates. */
+private val SUBTASK_STATE = arrayOf(
+    Tasks.ID, Tasks.ORIGINAL_INSTANCE_ID, Tasks.RRULE, Tasks.RDATE, Tasks.STATUS, Tasks.PERCENT_COMPLETE, Tasks.COMPLETED,
+    Tasks.DTSTART, Tasks.DUE, Tasks.IS_ALLDAY, Tasks.TZ, Tasks.UID,
+)
+
+/** What a tick changes on a series, and an undo changes back; with what its rule is read in. */
 private val SERIES_STATE = arrayOf(
     Tasks.DTSTART, Tasks.DUE, Tasks.DURATION, Tasks.RRULE, Tasks.RDATE, Tasks.EXDATE,
-    Tasks.STATUS, Tasks.COMPLETED, Tasks.PERCENT_COMPLETE,
+    Tasks.STATUS, Tasks.COMPLETED, Tasks.PERCENT_COMPLETE, Tasks.IS_ALLDAY, Tasks.TZ,
 )
 
 private const val TAG = "AndroidTasksDataSource"
@@ -950,5 +1089,3 @@ private const val TAG = "AndroidTasksDataSource"
 /** No rule to look up: the provider says the row does not recur. */
 private const val NO_RULE = -1L
 
-/** SQLite's default bound-argument limit on older Android releases. */
-private const val MAX_SQL_ARGS = 999

app/src/main/java/de/jeanlucmakiola/agendula/data/tasks/SqlChunks.kt

@@ -0,0 +1,23 @@
+package de.jeanlucmakiola.agendula.data.tasks
+
+/** SQLite's default bound-argument limit on older Android releases. */
+internal const val MAX_SQL_ARGS = 999
+
+/**
+ * `idColumn IN (…)` selections over [ids], each with its arguments and
+ * [filterArgs] after them, in chunks that keep every query within [limit]
+ * bound arguments.
+ */
+internal fun inSelections(
+    idColumn: String,
+    ids: Collection<Long>,
+    filter: String? = null,
+    filterArgs: List<String> = emptyList(),
+    limit: Int = MAX_SQL_ARGS,
+): List<Pair<String, Array<String>>> = ids.distinct().chunked(limit - filterArgs.size).map { chunk ->
+    val selection = buildString {
+        append("$idColumn IN (${chunk.joinToString(",") { "?" }})")
+        if (filter != null) append(" AND ($filter)")
+    }
+    selection to (chunk.map(Long::toString) + filterArgs).toTypedArray()
+}

app/src/main/java/de/jeanlucmakiola/agendula/data/tasks/SubtaskReset.kt

@@ -0,0 +1,266 @@
+package de.jeanlucmakiola.agendula.data.tasks
+
+import de.jeanlucmakiola.agendula.data.tasks.TasksContract.Tasks
+import de.jeanlucmakiola.agendula.domain.TaskStatus
+import de.jeanlucmakiola.agendula.domain.isClosed
+import de.jeanlucmakiola.agendula.domain.recurrence.ExpansionWindow
+import de.jeanlucmakiola.agendula.domain.recurrence.RecurrenceExpander
+import de.jeanlucmakiola.agendula.domain.recurrence.RecurrenceSpec
+import de.jeanlucmakiola.agendula.domain.recurrence.dateZone
+import de.jeanlucmakiola.agendula.domain.statusFromInt
+import java.time.Duration
+import java.time.LocalDateTime
+import java.time.ZoneId
+import java.time.temporal.ChronoUnit
+import kotlin.time.Duration.Companion.days
+import kotlin.time.Instant
+
+private const val MILLIS_PER_SECOND = 1000L
+private const val MILLIS_PER_DAY = 24L * 60 * 60 * 1000
+
+/** A sub-task's progress, which a routine's next occurrence starts without. */
+internal data class SubtaskState(val status: TaskStatus, val percent: Int?, val completedAt: Long?) {
+    /** Open with nothing done yet: what a reset leaves. */
+    val isFresh: Boolean get() = status == TaskStatus.NEEDS_ACTION && (percent ?: 0) == 0 && completedAt == null
+
+    companion object {
+        val FRESH = SubtaskState(TaskStatus.NEEDS_ACTION, null, null)
+    }
+}
+
+/** A sub-task's own start and due, as epoch millis. */
+internal data class SubtaskDates(val start: Long?, val due: Long?) {
+    val isEmpty: Boolean get() = start == null && due == null
+
+    /** The same dates as a store keeps them: to the second, or for an all-day task to the day. */
+    fun sameAs(other: SubtaskDates, isAllDay: Boolean): Boolean {
+        fun unit(at: Long?) = at?.let { Math.floorDiv(it, if (isAllDay) MILLIS_PER_DAY else MILLIS_PER_SECOND) }
+        return unit(start) == unit(other.start) && unit(due) == unit(other.due)
+    }
+
+    companion object {
+        val NONE = SubtaskDates(null, null)
+    }
+}
+
+/**
+ * A sub-task as [SubtaskReset] sees it; [recurring] also covers a copy a tick of
+ * a recurring one left. Its dates are read in [dateZone] of [isAllDay] and [timeZone].
+ */
+internal class SubtaskNode(
+    val id: Long,
+    val recurring: Boolean,
+    val state: SubtaskState,
+    val dates: SubtaskDates = SubtaskDates.NONE,
+    val isAllDay: Boolean = false,
+    val timeZone: String? = null,
+)
+
+/**
+ * A sub-task [SubtaskReset] reset: its state and dates before, and the dates the
+ * reset gave it. A record from before dates were kept has neither, and its dates
+ * are neither compared nor restored.
+ */
+internal data class ResetSubtask(
+    val id: Long,
+    val prior: SubtaskState,
+    val priorDates: SubtaskDates? = SubtaskDates.NONE,
+    val dates: SubtaskDates? = priorDates,
+)
+
+/** A reset sub-task as it is now, for [SubtaskReset.toRestore]. */
+internal class SubtaskNow(val state: SubtaskState, val dates: SubtaskDates, val isAllDay: Boolean)
+
+/** What moving a series back does with its reset sub-tasks: who gets their state back, and who changed since. */
+internal class SubtaskRestore(val restore: List<ResetSubtask>, val changed: List<Long>)
+
+/**
+ * How far a series moved in [seriesZone]: wall-clock time for a timed sub-task,
+ * so it keeps its place relative to the routine across a DST change, and the
+ * change of calendar date for an all-day one. [floating] reads a sub-task with
+ * no zone of its own.
+ */
+internal class SeriesShift(from: Long, to: Long, seriesZone: ZoneId, private val floating: ZoneId = ZoneId.systemDefault()) {
+    private val delta = Duration.between(local(from, seriesZone), local(to, seriesZone))
+    private val days = ChronoUnit.DAYS.between(local(from, seriesZone).toLocalDate(), local(to, seriesZone).toLocalDate())
+
+    /** [at] moved along. */
+    fun apply(at: Long, isAllDay: Boolean, timeZone: String? = null): Long {
+        val zone = dateZone(isAllDay, timeZone, floating)
+        val moved = if (isAllDay) local(at, zone).plusDays(days) else local(at, zone).plus(delta)
+        return moved.atZone(zone).toInstant().toEpochMilli()
+    }
+
+    private fun local(at: Long, zone: ZoneId) = LocalDateTime.ofInstant(java.time.Instant.ofEpochMilli(at), zone)
+}
+
+/**
+ * What a routine's sub-tasks do when its series moves on to the next occurrence
+ * (#160): the ones completed or in progress start over, as in tasks.org, dated
+ * ones move along with the routine, and moving the series back gives them their
+ * state and dates again.
+ */
+internal object SubtaskReset {
+
+    /** Only bounds the search for a next occurrence. */
+    private val LOOKAHEAD = (366 * 1000).days
+
+    /**
+     * The `X-` property Agendula puts on the copy a provider tick of a recurring
+     * sub-task left, valued with the UID of the parent it sits under, so any
+     * device knows it for one while it stays there.
+     */
+    const val COPY_MARKER = "X-AGENDULA-TICK-COPY"
+
+    /** The provider `properties` mimetype DAVx5 keeps unknown properties under, and round-trips. */
+    const val UNKNOWN_PROPERTY_MIMETYPE = "vnd.android.cursor.item/vnd.ical4android.unknown-property"
+
+    private val MARKER_JSON = Regex("""^\s*\[\s*"$COPY_MARKER"\s*,\s*"((?:[^"\\]|\\.)*)"""", RegexOption.IGNORE_CASE)
+
+    /** The marker for a copy under the parent [parentUid], as DAVx5 stores an unknown property: a JSON array of name and value. */
+    fun copyMarkerJson(parentUid: String): String =
+        "[\"$COPY_MARKER\",\"${parentUid.replace("\\", "\\\\").replace("\"", "\\\"")}\"]"
+
+    /** The parent UID an unknown-property row's JSON marks its task a copy under, or null when it is no marker. */
+    fun markerParentFromJson(json: String?): String? =
+        json?.let(MARKER_JSON::find)?.groupValues?.get(1)?.replace(Regex("""\\(.)"""), "$1")
+
+    /** The parent UID a stored residue's marker names, as a copy synced in from a provider install carries it. */
+    fun markerParentFromResidue(residue: String?): String? = residue?.lines()?.firstNotNullOfOrNull {
+        val line = it.trim()
+        val next = line.getOrNull(COPY_MARKER.length)
+        if (!line.startsWith(COPY_MARKER, ignoreCase = true) || (next != ':' && next != ';')) return@firstNotNullOfOrNull null
+        line.substringAfter(':').replace(Regex("""\\([\\;,])"""), "$1")
+    }
+
+    /** Whether a marker naming [markerParent] makes a task under [parentUid] a copy: only under the parent it came from. */
+    fun isCopyOf(markerParent: String?, parentUid: String?): Boolean = markerParent != null && markerParent == parentUid
+
+    /**
+     * The sub-tasks under [parentId], all the way down, to reset: started ones,
+     * and with a [shift], dated ones too. A recurring one has a series of its
+     * own and is left alone with everything under it; a cancelled one stays as
+     * it is.
+     */
+    fun toReset(parentId: Long, shift: SeriesShift? = null, children: (Long) -> List<SubtaskNode>): List<ResetSubtask> {
+        val seen = mutableSetOf(parentId)
+        val reset = mutableListOf<ResetSubtask>()
+        fun walk(id: Long) {
+            children(id).filter { !it.recurring && seen.add(it.id) }.forEach {
+                val moves = shift != null && !it.dates.isEmpty
+                if (it.state.status != TaskStatus.CANCELLED && (!it.state.isFresh || moves)) {
+                    val dates = if (shift == null) it.dates else SubtaskDates(
+                        it.dates.start?.let { at -> shift.apply(at, it.isAllDay, it.timeZone) },
+                        it.dates.due?.let { at -> shift.apply(at, it.isAllDay, it.timeZone) },
+                    )
+                    reset += ResetSubtask(it.id, it.state, it.dates, dates)
+                }
+                walk(it.id)
+            }
+        }
+        walk(parentId)
+        return reset
+    }
+
+    /**
+     * A provider row as a node. Nothing the provider sets on a detached copy marks
+     * it as one, so a copy is known by the [copies] ticks on this install left, or
+     * by a [markerParent] naming the [parentUid] it sits under: it belongs to a
+     * recurring sub-task and counts as recurring.
+     */
+    fun providerNode(
+        id: Long,
+        rrule: String?,
+        rdate: String?,
+        copies: Set<Long>,
+        markerParent: String? = null,
+        parentUid: String? = null,
+        state: SubtaskState,
+        dates: SubtaskDates = SubtaskDates.NONE,
+        isAllDay: Boolean = false,
+        timeZone: String? = null,
+    ) = SubtaskNode(
+        id,
+        !rrule.isNullOrBlank() || !rdate.isNullOrBlank() || id in copies || isCopyOf(markerParent, parentUid),
+        state, dates, isAllDay, timeZone,
+    )
+
+    /**
+     * The reset sub-tasks still as the reset left them, so moving back may
+     * restore them, and the ones changed since, which keep the user's state.
+     * A deleted one is neither.
+     */
+    fun toRestore(reset: List<ResetSubtask>, current: (Long) -> SubtaskNow?): SubtaskRestore {
+        val restore = mutableListOf<ResetSubtask>()
+        val changed = mutableListOf<Long>()
+        reset.forEach { entry ->
+            val now = current(entry.id) ?: return@forEach
+            val unchanged = now.state.isFresh && (entry.dates == null || now.dates.sameAs(entry.dates, now.isAllDay))
+            if (unchanged) restore += entry else changed += entry.id
+        }
+        return SubtaskRestore(restore, changed)
+    }
+
+    fun encode(reset: List<ResetSubtask>): String = reset.joinToString(";") {
+        listOf(
+            it.id, it.prior.status.name, it.prior.percent, it.prior.completedAt,
+            it.priorDates?.start, it.priorDates?.due, it.dates?.start, it.dates?.due,
+        ).joinToString(",") { value -> value?.toString().orEmpty() }
+    }
+
+    fun decode(raw: String?): List<ResetSubtask> = raw.orEmpty().split(';').mapNotNull { entry ->
+        val parts = entry.split(',')
+        if (parts.size != 4 && parts.size != 8) return@mapNotNull null
+        val id = parts[0].toLongOrNull() ?: return@mapNotNull null
+        val status = TaskStatus.entries.firstOrNull { it.name == parts[1] } ?: return@mapNotNull null
+        val state = SubtaskState(status, parts[2].toIntOrNull(), parts[3].toLongOrNull())
+        if (parts.size == 4) return@mapNotNull ResetSubtask(id, state, priorDates = null, dates = null)
+        ResetSubtask(
+            id, state,
+            SubtaskDates(parts[4].toLongOrNull(), parts[5].toLongOrNull()),
+            SubtaskDates(parts[6].toLongOrNull(), parts[7].toLongOrNull()),
+        )
+    }
+
+    /** A provider series' rule set from its columns. */
+    fun specOf(state: Map<String, Any?>): RecurrenceSpec? = TaskMapper.seriesSpec(MapColumnReader(state))
+
+    /** How the series moved from [before] to [after], read in the zone its rule is expanded in. */
+    fun shiftOf(before: Map<String, Any?>, after: Map<String, Any?>, floating: ZoneId = ZoneId.systemDefault()): SeriesShift? {
+        val from = anchor(before) ?: return null
+        val to = anchor(after) ?: return null
+        val reader = MapColumnReader(after)
+        return SeriesShift(from, to, dateZone(reader.getBoolean(Tasks.IS_ALLDAY), reader.getString(Tasks.TZ), floating), floating)
+    }
+
+    /**
+     * Whether a provider tick moved the series on, judged by its columns
+     * [before] and [after]: its start (or due) moved later and it is still open,
+     * with [next], its rule set as it now stands, generating an occurrence from
+     * there. An `EXDATE` or a status alone is no move; a series whose rule ran
+     * out is finished.
+     */
+    fun movedOn(before: Map<String, Any?>?, after: Map<String, Any?>?, next: RecurrenceSpec? = after?.let(::specOf)): Boolean {
+        val was = anchor(before ?: return false) ?: return false
+        val now = anchor(after ?: return false) ?: return false
+        if (now <= was) return false
+        if (statusFromInt((after[Tasks.STATUS] as? Number)?.toInt()).isClosed) return false
+        val spec = next ?: return false
+        if (spec.rrule == null && spec.rdate == null) return false
+        val parts = spec.rrule?.split(';')?.map { it.trim() }?.filter { it.isNotEmpty() }
+        val count = parts?.firstOrNull { it.startsWith("COUNT=", ignoreCase = true) }?.substringAfter('=')?.toIntOrNull()
+        if (count != null && count <= 0) return false
+        // Expanded from the old start, as an expansion always yields its own start
+        // even past UNTIL. COUNT is left out: it was spent before the new start.
+        val probe = spec.copy(
+            rrule = parts?.filterNot { it.startsWith("COUNT=", ignoreCase = true) }?.joinToString(";"),
+            anchor = Instant.fromEpochMilliseconds(was),
+        )
+        val from = Instant.fromEpochMilliseconds(now)
+        return RecurrenceExpander.expand(probe, ExpansionWindow(from = from, until = from + LOOKAHEAD, maxOccurrences = 1)).isNotEmpty()
+    }
+
+    /** The anchor a series' columns put it at: its start, or else its due date. */
+    fun anchor(state: Map<String, Any?>): Long? =
+        (state[Tasks.DTSTART] as? Number)?.toLong() ?: (state[Tasks.DUE] as? Number)?.toLong()
+}

app/src/main/java/de/jeanlucmakiola/agendula/data/tasks/TaskMapper.kt

@@ -8,6 +8,7 @@ import de.jeanlucmakiola.agendula.domain.TaskList
 import de.jeanlucmakiola.agendula.domain.export.ExportTask
 import de.jeanlucmakiola.agendula.domain.priorityFromICal
 import de.jeanlucmakiola.agendula.domain.statusFromInt
+import de.jeanlucmakiola.agendula.domain.recurrence.RecurrenceSpec
 import kotlin.time.Instant
 
 /** Maps a provider row (via [ColumnReader]) to a domain model. Pure + testable. */
@@ -77,6 +78,20 @@ object TaskMapper {
         return if (rrule == null && rdate == null) null else SeriesRule(rrule, rdate)
     }
 
+    /** The rule set of a `tasks` row, anchored on its start or else its due date; null without either date. */
+    fun seriesSpec(r: ColumnReader): RecurrenceSpec? {
+        val rule = seriesRule(r)
+        val anchor = r.getLong(Tasks.DTSTART) ?: r.getLong(Tasks.DUE) ?: return null
+        return RecurrenceSpec(
+            rrule = rule?.rrule,
+            rdate = rule?.rdate,
+            exdate = r.getString(Tasks.EXDATE),
+            anchor = Instant.fromEpochMilliseconds(anchor),
+            isAllDay = r.getBoolean(Tasks.IS_ALLDAY),
+            timeZone = r.getString(Tasks.TZ),
+        )
+    }
+
     /**
      * The occurrence's `RECURRENCE-ID` anchor.
      *

app/src/main/java/de/jeanlucmakiola/agendula/data/tasks/TickResets.kt

@@ -0,0 +1,42 @@
+package de.jeanlucmakiola.agendula.data.tasks
+
+import android.content.SharedPreferences
+
+/**
+ * The sub-tasks a provider tick reset, as [SubtaskReset.encode] writes them,
+ * kept for [TickedCopies.HORIZON_MS] under the series and the anchor the tick
+ * moved it to: whether or not the provider left a copy that [TickedCopies]
+ * could record, moving the series back from there finds them.
+ */
+internal class TickResets(private val prefs: () -> SharedPreferences) {
+
+    fun put(authority: String, seriesId: Long, anchor: Long, reset: String, at: Long) {
+        val stale = expire(prefs().all, at)
+        prefs().edit().apply {
+            stale.forEach(::remove)
+            putString(key(authority, seriesId, anchor), encode(at, reset))
+        }.apply()
+    }
+
+    fun get(authority: String, seriesId: Long, anchor: Long): String? =
+        prefs().getString(key(authority, seriesId, anchor), null)?.let(::decode)
+
+    fun remove(authority: String, seriesId: Long, anchor: Long) {
+        prefs().edit().remove(key(authority, seriesId, anchor)).apply()
+    }
+
+    companion object {
+        fun key(authority: String, seriesId: Long, anchor: Long) = "$authority|$seriesId|$anchor"
+
+        fun encode(at: Long, reset: String) = "$at|$reset"
+
+        /** The reset an entry holds, or null when it is not one. */
+        fun decode(raw: String): String? = raw.substringBefore('|', "").toLongOrNull()?.let { raw.substringAfter('|') }
+
+        /** The keys of [entries] past the horizon at [now], unreadable ones included. */
+        fun expire(entries: Map<String, *>, now: Long): Set<String> = entries.filter { (_, value) ->
+            val at = (value as? String)?.substringBefore('|', "")?.toLongOrNull() ?: 0L
+            now - at > TickedCopies.HORIZON_MS
+        }.keys
+    }
+}

app/src/main/java/de/jeanlucmakiola/agendula/data/tasks/TickedCopies.kt

@@ -7,6 +7,7 @@ import kotlin.time.Instant
 /**
  * What ticking a provider occurrence left: the copy the provider detached, and
  * the series' columns before and after the tick, so an undo can move it back.
+ * The sub-tasks it reset are kept apart, in [TickResets].
  */
 internal class Tick(
     val copyId: Long,
@@ -16,8 +17,12 @@ internal class Tick(
     val at: Long,
 )
 
-/** The provider keeps no record of its ticks, so they are kept here for [HORIZON_MS]. */
-internal class TickedCopies(private val prefs: () -> SharedPreferences) {
+/**
+ * The provider keeps no record of its ticks, so they are kept here for
+ * [HORIZON_MS]. The copies' ids are kept for good in [known]: a detached copy
+ * carries nothing that marks it as one.
+ */
+internal class TickedCopies(private val prefs: () -> SharedPreferences, private val known: () -> SharedPreferences) {
 
     fun key(authority: String, taskId: Long, occurrenceStart: Instant) =
         "$authority|$taskId|${wholeSecond(occurrenceStart).epochSeconds}"
@@ -31,21 +36,40 @@ internal class TickedCopies(private val prefs: () -> SharedPreferences) {
             (value as? String)?.let(::decode)?.takeIf { it.copyId == copyId }?.let { key to it }
         }
 
+    /** Every copy a tick in Agendula left in [authority]. */
+    fun copies(authority: String): Set<Long> {
+        val kept = knownIds(authority).mapNotNullTo(HashSet()) { it.toLongOrNull() }
+        prefs().all.forEach { (key, value) ->
+            if (key.startsWith("$authority|")) (value as? String)?.let(::decode)?.let { kept += it.copyId }
+        }
+        return kept
+    }
+
+    /** Records [tick] under [key]; ticks past [HORIZON_MS] go, their copies stay known. */
     fun put(key: String, tick: Tick) {
-        val stale = prefs().all.filter { (_, value) ->
-            val at = (value as? String)?.let(::decode)?.at ?: 0L
-            tick.at - at > HORIZON_MS
-        }.keys
+        val (stale, keep) = expire(prefs().all.mapValues { (_, value) -> (value as? String)?.let(::decode) }, tick.at)
+        val known = keep + (key.substringBefore('|') to (keep[key.substringBefore('|')].orEmpty() + tick.copyId))
+        known().edit().apply {
+            known.forEach { (authority, ids) -> putStringSet(authority, knownIds(authority) + ids.map(Long::toString)) }
+        }.apply()
         prefs().edit().apply {
             stale.forEach(::remove)
             putString(key, encode(tick))
         }.apply()
     }
 
+    /** Drops the tick under [key], and its copy from the known ones: moving back deleted it, and its id may be reused. */
     fun remove(key: String) {
+        val copy = get(key)?.copyId
         prefs().edit().remove(key).apply()
+        if (copy != null) {
+            val authority = key.substringBefore('|')
+            known().edit().putStringSet(authority, knownIds(authority) - copy.toString()).apply()
+        }
     }
 
+    private fun knownIds(authority: String): Set<String> = known().getStringSet(authority, emptySet()).orEmpty().toSet()
+
     private fun encode(tick: Tick): String = JSONObject().apply {
         put("copy", tick.copyId)
         put("at", tick.at)
@@ -80,5 +104,16 @@ internal class TickedCopies(private val prefs: () -> SharedPreferences) {
     companion object {
         /** As long as the own store keeps a tick undoable. */
         const val HORIZON_MS = 30L * 24 * 60 * 60 * 1000
+
+        /**
+         * The keys of [ticks] past the horizon at [now], unreadable ones included,
+         * and per authority the copies they leave, which stay known after the tick goes.
+         */
+        fun expire(ticks: Map<String, Tick?>, now: Long): Pair<Set<String>, Map<String, Set<Long>>> {
+            val stale = ticks.filter { (_, tick) -> now - (tick?.at ?: 0L) > HORIZON_MS }
+            val keep = stale.entries.mapNotNull { (key, tick) -> tick?.let { key.substringBefore('|') to it.copyId } }
+                .groupBy({ it.first }, { it.second }).mapValues { it.value.toSet() }
+            return stale.keys to keep
+        }
     }
 }

app/src/main/java/de/jeanlucmakiola/agendula/data/tasks/room/AdvancedOccurrence.kt

@@ -51,6 +51,8 @@ data class AdvancedOccurrenceEntity(
     @ColumnInfo(name = "undoable", defaultValue = "1") val undoable: Boolean = true,
     /** Set once the moved series reached the server, which then holds the move itself. */
     @ColumnInfo(name = "settled", defaultValue = "0") val settled: Boolean = false,
+    /** The series' sub-tasks the move reset, with their state before, as [de.jeanlucmakiola.agendula.data.tasks.SubtaskReset.encode] writes them. */
+    @ColumnInfo(name = "reset_subtasks", defaultValue = "") val resetSubtasks: String = "",
 ) {
     val dropped: List<Instant>
         get() = droppedExdates.split(',').mapNotNull { it.toLongOrNull()?.let(Instant::fromEpochMilliseconds) }

app/src/main/java/de/jeanlucmakiola/agendula/data/tasks/room/RoomTasksDataSource.kt

@@ -1,6 +1,14 @@
 package de.jeanlucmakiola.agendula.data.tasks.room
 
+import android.util.Log
 import androidx.room.InvalidationTracker
+import de.jeanlucmakiola.agendula.data.tasks.ResetSubtask
+import de.jeanlucmakiola.agendula.data.tasks.SeriesShift
+import de.jeanlucmakiola.agendula.data.tasks.SubtaskDates
+import de.jeanlucmakiola.agendula.data.tasks.SubtaskNode
+import de.jeanlucmakiola.agendula.data.tasks.SubtaskNow
+import de.jeanlucmakiola.agendula.data.tasks.SubtaskReset
+import de.jeanlucmakiola.agendula.data.tasks.SubtaskState
 import de.jeanlucmakiola.agendula.data.tasks.TaskQuery
 import de.jeanlucmakiola.agendula.domain.TaskReminder
 import de.jeanlucmakiola.agendula.domain.TaskReminderOrder
@@ -18,6 +26,7 @@ import de.jeanlucmakiola.agendula.domain.recurrence.ExpansionWindow
 import de.jeanlucmakiola.agendula.domain.recurrence.RecurrenceExpander
 import de.jeanlucmakiola.agendula.domain.recurrence.RecurrenceSpec
 import java.time.ZoneId
+import de.jeanlucmakiola.agendula.domain.recurrence.dateZone
 import java.util.UUID
 import javax.inject.Inject
 import javax.inject.Singleton
@@ -91,6 +100,8 @@ private val TASK_TABLES = arrayOf("tasks", "task_lists", "task_alarms")
 /** Distinct alarm texts whose `ACKNOWLEDGED` is remembered between scheduler passes. */
 private const val ACK_CACHE_SIZE = 512
 
+private const val TAG = "RoomTasksDataSource"
+
 /**
  * [TasksDataSource] over Agendula's own Room store.
  *
@@ -638,6 +649,7 @@ class RoomTasksDataSource @Inject constructor(
                 isDirty = true,
             ),
         )
+        val (reset, resetLists) = resetSubtasks(master, newAnchor, now)
         val copyId = if (override != null) {
             detach(override, now, close)
         } else {
@@ -663,13 +675,66 @@ class RoomTasksDataSource @Inject constructor(
                 ruleAfter = ruleAfter,
                 droppedExdates = AdvancedOccurrenceEntity.encode(TaskFormWriter.instantsBefore(master.exdate, newAnchor, zone)),
                 fromOverride = override != null,
+                resetSubtasks = SubtaskReset.encode(reset),
             ),
         )
         advanced.insertDetached(detached.map { (at, id) -> AdvancedDetachedEntity(copyId = copyId, anchor = at, taskId = id) })
-        writes.onWritten(setOf(master.listId))
+        writes.onWritten(setOf(master.listId) + resetLists)
         return true
     }
 
+    /**
+     * Resets what [SubtaskReset] picks under [master] for the series' next
+     * occurrence at [newAnchor], dated ones moved along; the lists it wrote to.
+     * A copy a provider tick of a recurring sub-task left, synced in, is known by
+     * its marker while it stays under the parent the marker names.
+     */
+    private fun resetSubtasks(master: TaskEntity, newAnchor: Instant, now: Instant): Pair<List<ResetSubtask>, Set<Long>> {
+        val floating = ZoneId.of(zone())
+        val shift = master.recurrenceAnchor?.let {
+            SeriesShift(it.toEpochMilliseconds(), newAnchor.toEpochMilliseconds(), dateZone(master.isAllDay, master.timezone, floating), floating)
+        }
+        val loaded = HashMap<Long, TaskEntity>().apply { put(master.id, master) }
+        val reset = SubtaskReset.toReset(master.id, shift) { id ->
+            val parentUid = loaded[id]?.uid
+            tasks.subtasks(id).map { row ->
+                val sub = row.task.also { loaded[it.id] = it }
+                val copy = SubtaskReset.isCopyOf(SubtaskReset.markerParentFromResidue(sub.unknownProperties), parentUid)
+                SubtaskNode(sub.id, sub.isRecurring || copy, sub.progress, sub.dates, sub.isAllDay, sub.timezone)
+            }
+        }
+        val lists = reset.mapNotNull { entry ->
+            loaded[entry.id]?.also { tasks.update(it.withProgress(SubtaskState.FRESH, entry.dates, now)) }?.listId
+        }
+        return reset to lists.toSet()
+    }
+
+    /** What [resetSubtasks] reset for [record], back as it was where nothing changed it since. */
+    private fun restoreSubtasks(record: AdvancedOccurrenceEntity, now: Instant): Set<Long> {
+        val entries = SubtaskReset.decode(record.resetSubtasks)
+        val current = entries.mapNotNull { entry -> tasks.entity(entry.id)?.takeUnless { it.isDeleted } }.associateBy { it.id }
+        val outcome = SubtaskReset.toRestore(entries) { id -> current[id]?.let { SubtaskNow(it.progress, it.dates, it.isAllDay) } }
+        if (outcome.changed.isNotEmpty()) Log.i(TAG, "Sub-tasks ${outcome.changed} changed since the reset and keep their state")
+        return outcome.restore.mapNotNull { entry ->
+            current[entry.id]?.also { tasks.update(it.withProgress(entry.prior, entry.priorDates, now)) }?.listId
+        }.toSet()
+    }
+
+    private val TaskEntity.progress get() = SubtaskState(status, percentComplete, completedAt?.toEpochMilliseconds())
+
+    private val TaskEntity.dates get() = SubtaskDates(dtstart?.toEpochMilliseconds(), due?.toEpochMilliseconds())
+
+    /** [state] onto the row, and [dates] unless they are unknown. */
+    private fun TaskEntity.withProgress(state: SubtaskState, dates: SubtaskDates?, now: Instant) = copy(
+        status = state.status,
+        percentComplete = state.percent,
+        completedAt = state.completedAt?.let(Instant::fromEpochMilliseconds),
+        dtstart = if (dates == null) dtstart else dates.start?.let(Instant::fromEpochMilliseconds),
+        due = if (dates == null) due else dates.due?.let(Instant::fromEpochMilliseconds),
+        lastModified = now,
+        isDirty = true,
+    )
+
     /** Occurrences `COUNT` has spent before [cut]: counted before `EXDATE` (RFC 5545 §3.8.5.3). */
     private fun spentBefore(spec: RecurrenceSpec, cut: Instant): Int = RecurrenceExpander.expand(
         spec.copy(exdate = null),
@@ -754,7 +819,7 @@ class RoomTasksDataSource @Inject constructor(
         val plain = reopened.status == TaskStatus.NEEDS_ACTION && reopened.percentComplete == null
         if (record.fromOverride || !plain) toOverride(reopened, back, record.anchor, now)
         else deleteTask(row.id)
-        writes.onWritten(setOf(master.listId))
+        writes.onWritten(setOf(master.listId) + restoreSubtasks(record, now))
         return true
     }
 

app/src/main/java/de/jeanlucmakiola/agendula/data/tasks/room/TasksDatabase.kt

@@ -24,7 +24,7 @@ import kotlin.time.Instant
         AdvancedOccurrenceEntity::class,
         AdvancedDetachedEntity::class,
     ],
-    version = 5,
+    version = 6,
     exportSchema = true,
 )
 @TypeConverters(Converters::class)
@@ -204,5 +204,12 @@ abstract class TasksDatabase : RoomDatabase() {
                 )
             }
         }
+
+        /** v6 remembers which sub-tasks a moved series reset, so moving it back restores them (#160). */
+        val MIGRATION_5_6 = object : Migration(5, 6) {
+            override fun migrate(db: SupportSQLiteDatabase) {
+                db.execSQL("ALTER TABLE advanced_occurrences ADD COLUMN `reset_subtasks` TEXT NOT NULL DEFAULT ''")
+            }
+        }
     }
 }

app/src/main/java/de/jeanlucmakiola/agendula/domain/recurrence/RecurrenceExpander.kt

@@ -12,6 +12,16 @@ import kotlin.time.Instant
 private const val MILLIS_PER_SECOND = 1000L
 private const val MILLIS_PER_DAY = 24L * 60 * 60 * 1000
 
+/**
+ * The zone a task's dates are read in: UTC for an all-day one, whose dates are
+ * midnights there; else its [timeZone], or [floating] when it has none or an
+ * unknown one.
+ */
+fun dateZone(isAllDay: Boolean, timeZone: String?, floating: ZoneId = ZoneId.systemDefault()): ZoneId {
+    if (isAllDay) return ZoneId.of("UTC")
+    return timeZone?.let { runCatching { ZoneId.of(it) }.getOrNull() } ?: floating
+}
+
 /** The rule set of one task series, as stored. All strings are raw iCalendar values. */
 data class RecurrenceSpec(
     val rrule: String?,
@@ -133,11 +143,8 @@ object RecurrenceExpander {
         return occurrences.indices.map { it - current }
     }
 
-    private fun zoneOf(spec: RecurrenceSpec, floatingZone: ZoneId): TimeZone {
-        if (spec.isAllDay) return TimeZone.getTimeZone(ZoneId.of("UTC"))
-        val stored = spec.timeZone?.let { runCatching { ZoneId.of(it) }.getOrNull() }
-        return TimeZone.getTimeZone(stored ?: floatingZone)
-    }
+    private fun zoneOf(spec: RecurrenceSpec, floatingZone: ZoneId): TimeZone =
+        TimeZone.getTimeZone(dateZone(spec.isAllDay, spec.timeZone, floatingZone))
 
     /**
      * All-day series are date-anchored: pin the anchor to UTC midnight, as it is

app/src/test/java/de/jeanlucmakiola/agendula/data/tasks/SqlChunksTest.kt

@@ -0,0 +1,24 @@
+package de.jeanlucmakiola.agendula.data.tasks
+
+import com.google.common.truth.Truth.assertThat
+import org.junit.jupiter.api.Test
+
+class SqlChunksTest {
+
+    @Test
+    fun `ids are split so no query binds more than the limit`() {
+        val ids = (1L..2_100L).toList()
+        val chunks = inSelections("_id", ids, filter = "deleted = ?", filterArgs = listOf("0"))
+
+        assertThat(chunks.map { it.second.size }).containsExactly(999, 999, 105).inOrder()
+        assertThat(chunks.flatMap { (_, args) -> args.dropLast(1) }).isEqualTo(ids.map(Long::toString))
+        assertThat(chunks.all { (_, args) -> args.last() == "0" }).isTrue()
+        assertThat(chunks.first().first).endsWith("?) AND (deleted = ?)")
+    }
+
+    @Test
+    fun `repeated ids are bound once, and none give no query`() {
+        assertThat(inSelections("_id", listOf(3L, 3L, 4L)).single().second).asList().containsExactly("3", "4")
+        assertThat(inSelections("_id", emptyList())).isEmpty()
+    }
+}

app/src/test/java/de/jeanlucmakiola/agendula/data/tasks/SubtaskResetTest.kt

@@ -0,0 +1,299 @@
+package de.jeanlucmakiola.agendula.data.tasks
+
+import com.google.common.truth.Truth.assertThat
+import de.jeanlucmakiola.agendula.data.tasks.TasksContract.Tasks
+import de.jeanlucmakiola.agendula.domain.TaskStatus
+import de.jeanlucmakiola.agendula.domain.recurrence.RecurrenceSpec
+import org.junit.jupiter.api.Test
+import java.time.ZoneId
+import java.time.ZoneOffset
+import kotlin.time.Instant
+
+class SubtaskResetTest {
+
+    private val done = SubtaskState(TaskStatus.COMPLETED, 100, 1_000L)
+    private val halfway = SubtaskState(TaskStatus.IN_PROCESS, 50, null)
+    private val cancelled = SubtaskState(TaskStatus.CANCELLED, null, null)
+
+    private fun node(id: Long, state: SubtaskState = done, recurring: Boolean = false) = SubtaskNode(id, recurring, state)
+
+    private fun reset(vararg tree: Pair<Long, List<SubtaskNode>>): List<Long> {
+        val children = tree.toMap()
+        return SubtaskReset.toReset(1L) { children[it].orEmpty() }.map { it.id }
+    }
+
+    @Test
+    fun `completed and half-done sub-tasks of a routine start over, fresh ones are left (#160)`() {
+        val reopened = reset(1L to listOf(node(2), node(3, SubtaskState.FRESH), node(4, halfway)))
+        assertThat(reopened).containsExactly(2L, 4L)
+    }
+
+    @Test
+    fun `an open sub-task with progress counts as started`() {
+        assertThat(reset(1L to listOf(node(2, SubtaskState(TaskStatus.NEEDS_ACTION, 20, null))))).containsExactly(2L)
+    }
+
+    @Test
+    fun `a cancelled sub-task stays cancelled, what is under it still starts over`() {
+        assertThat(reset(1L to listOf(node(2, cancelled)), 2L to listOf(node(3)))).containsExactly(3L)
+    }
+
+    @Test
+    fun `nested sub-tasks start over too, also under a fresh one`() {
+        val reopened = reset(
+            1L to listOf(node(2, SubtaskState.FRESH)),
+            2L to listOf(node(3)),
+            3L to listOf(node(4)),
+        )
+        assertThat(reopened).containsExactly(3L, 4L)
+    }
+
+    @Test
+    fun `a recurring sub-task, or a copy a tick of one left, is left alone with what is under it`() {
+        val reopened = reset(
+            1L to listOf(node(2, recurring = true), node(3), node(5, recurring = true)),
+            2L to listOf(node(4)),
+        )
+        assertThat(reopened).containsExactly(3L)
+    }
+
+    @Test
+    fun `a provider copy a tick in Agendula left is left alone, a plain sub-task is not`() {
+        val copies = setOf(3L)
+        val rows = listOf(
+            SubtaskReset.providerNode(2, rrule = "FREQ=DAILY", rdate = null, copies = copies, state = done),
+            SubtaskReset.providerNode(3, rrule = null, rdate = null, copies = copies, state = done),
+            SubtaskReset.providerNode(4, rrule = null, rdate = "20261110T080000Z", copies = copies, state = done),
+            SubtaskReset.providerNode(5, rrule = " ", rdate = null, copies = copies, state = done),
+        )
+        assertThat(SubtaskReset.toReset(1L) { if (it == 1L) rows else emptyList() }.map { it.id }).containsExactly(5L)
+    }
+
+    @Test
+    fun `a cycle or the parent listed under itself is not walked twice`() {
+        val reopened = reset(
+            1L to listOf(node(1), node(2)),
+            2L to listOf(node(3)),
+            3L to listOf(node(2)),
+        )
+        assertThat(reopened).containsExactly(2L, 3L)
+    }
+
+    @Test
+    fun `what was reset survives encoding`() {
+        val reset = listOf(
+            ResetSubtask(2, done),
+            ResetSubtask(3, halfway, SubtaskDates(1L, 2L), SubtaskDates(11L, 12L)),
+            ResetSubtask(4, SubtaskState(TaskStatus.NEEDS_ACTION, 10, null), SubtaskDates(null, 5L), SubtaskDates(null, 15L)),
+        )
+        assertThat(SubtaskReset.decode(SubtaskReset.encode(reset))).isEqualTo(reset)
+        assertThat(SubtaskReset.decode("")).isEmpty()
+        assertThat(SubtaskReset.decode(null)).isEmpty()
+        assertThat(SubtaskReset.decode("x,COMPLETED,,;2,NOPE,,;3,IN_PROCESS")).isEmpty()
+    }
+
+    @Test
+    fun `a record from before dates were kept restores the state and leaves the dates`() {
+        val legacy = SubtaskReset.decode("2,COMPLETED,100,1000").single()
+        assertThat(legacy).isEqualTo(ResetSubtask(2, done, priorDates = null, dates = null))
+
+        val dated = SubtaskNow(SubtaskState.FRESH, SubtaskDates(at("2026-11-09T10:00:00Z"), null), isAllDay = false)
+        assertThat(SubtaskReset.toRestore(listOf(legacy)) { dated }.restore).containsExactly(legacy)
+        assertThat(SubtaskReset.encode(listOf(legacy))).isEqualTo("2,COMPLETED,100,1000,,,,")
+    }
+
+    private fun now(state: SubtaskState, dates: SubtaskDates = SubtaskDates.NONE, allDay: Boolean = false) = SubtaskNow(state, dates, allDay)
+
+    @Test
+    fun `moving back restores only the sub-tasks still as the reset left them`() {
+        val moved = SubtaskDates(20_000L, null)
+        val reset = listOf(
+            ResetSubtask(2, done),
+            ResetSubtask(3, halfway),
+            ResetSubtask(4, done),
+            ResetSubtask(5, done, SubtaskDates(10_000L, null), moved),
+            ResetSubtask(6, done, SubtaskDates(10_000L, null), moved),
+        )
+        val current = mapOf(
+            2L to now(SubtaskState.FRESH),
+            3L to now(done),
+            5L to now(SubtaskState.FRESH, moved),
+            // Re-dated since: the user's dates win.
+            6L to now(SubtaskState.FRESH, SubtaskDates(30_000L, null)),
+        )
+        val outcome = SubtaskReset.toRestore(reset, current::get)
+        assertThat(outcome.restore.map { it.id }).containsExactly(2L, 5L)
+        // 4 is gone: neither restored nor reported as changed.
+        assertThat(outcome.changed).containsExactly(3L, 6L)
+    }
+
+    @Test
+    fun `dates compare as a store keeps them, to the second or the day`() {
+        val reset = ResetSubtask(2, done, SubtaskDates.NONE, SubtaskDates(at("2026-11-09T10:00:00.250Z"), null))
+        val allDay = ResetSubtask(3, done, SubtaskDates.NONE, SubtaskDates(null, at("2026-11-10T00:00:00Z")))
+        fun restores(entry: ResetSubtask, stored: Long, isAllDay: Boolean) =
+            SubtaskReset.toRestore(listOf(entry)) { now(SubtaskState.FRESH, SubtaskDates(if (isAllDay) null else stored, if (isAllDay) stored else null), isAllDay) }
+                .restore.isNotEmpty()
+
+        assertThat(restores(reset, at("2026-11-09T10:00:00Z"), isAllDay = false)).isTrue()
+        assertThat(restores(reset, at("2026-11-09T10:00:01Z"), isAllDay = false)).isFalse()
+        assertThat(restores(allDay, at("2026-11-10T12:00:00Z"), isAllDay = true)).isTrue()
+        assertThat(restores(allDay, at("2026-11-11T00:00:00Z"), isAllDay = true)).isFalse()
+    }
+
+    private val berlin = ZoneId.of("Europe/Berlin")
+
+    private fun at(text: String) = java.time.Instant.parse(text).toEpochMilli()
+
+    @Test
+    fun `a dated sub-task keeps its wall-clock place to the routine across a DST change`() {
+        // A weekly routine at 09:00 Berlin moves from the last Monday of summer time to the first of winter time.
+        val shift = SeriesShift(at("2026-10-19T07:00:00Z"), at("2026-10-26T08:00:00Z"), berlin, floating = ZoneOffset.UTC)
+        assertThat(shift.apply(at("2026-10-20T08:00:00Z"), isAllDay = false, timeZone = "Europe/Berlin")).isEqualTo(at("2026-10-27T09:00:00Z"))
+        assertThat(shift.apply(at("2026-10-21T00:00:00Z"), isAllDay = true)).isEqualTo(at("2026-10-28T00:00:00Z"))
+    }
+
+    @Test
+    fun `an all-day sub-task follows the routine's change of date, also on a step under a day`() {
+        // An eight-hourly routine moves from 20:00 to 04:00 the next day in Berlin.
+        val shift = SeriesShift(at("2026-11-09T19:00:00Z"), at("2026-11-10T03:00:00Z"), berlin, floating = ZoneOffset.UTC)
+        assertThat(shift.apply(at("2026-11-09T00:00:00Z"), isAllDay = true)).isEqualTo(at("2026-11-10T00:00:00Z"))
+        // From 04:00 to 12:00 the date stays.
+        val sameDay = SeriesShift(at("2026-11-10T03:00:00Z"), at("2026-11-10T11:00:00Z"), berlin, floating = ZoneOffset.UTC)
+        assertThat(sameDay.apply(at("2026-11-10T00:00:00Z"), isAllDay = true)).isEqualTo(at("2026-11-10T00:00:00Z"))
+    }
+
+    @Test
+    fun `a timed sub-task without a zone of its own is read in the floating zone`() {
+        val shift = SeriesShift(at("2026-10-19T07:00:00Z"), at("2026-10-26T08:00:00Z"), berlin, floating = berlin)
+        assertThat(shift.apply(at("2026-10-20T08:00:00Z"), isAllDay = false)).isEqualTo(at("2026-10-27T09:00:00Z"))
+    }
+
+    @Test
+    fun `moving on shifts dated sub-tasks, fresh ones included, and leaves undated fresh ones`() {
+        val shift = SeriesShift(at("2026-11-02T08:00:00Z"), at("2026-11-09T08:00:00Z"), ZoneOffset.UTC, floating = ZoneOffset.UTC)
+        val nodes = listOf(
+            SubtaskNode(2, false, done, SubtaskDates(at("2026-11-02T10:00:00Z"), null)),
+            SubtaskNode(3, false, SubtaskState.FRESH, SubtaskDates(null, at("2026-11-03T00:00:00Z")), isAllDay = true),
+            SubtaskNode(4, false, SubtaskState.FRESH),
+            SubtaskNode(5, false, cancelled, SubtaskDates(at("2026-11-02T10:00:00Z"), null)),
+        )
+        val reset = SubtaskReset.toReset(1L, shift) { if (it == 1L) nodes else emptyList() }
+        assertThat(reset).containsExactly(
+            ResetSubtask(2, done, SubtaskDates(at("2026-11-02T10:00:00Z"), null), SubtaskDates(at("2026-11-09T10:00:00Z"), null)),
+            ResetSubtask(3, SubtaskState.FRESH, SubtaskDates(null, at("2026-11-03T00:00:00Z")), SubtaskDates(null, at("2026-11-10T00:00:00Z"))),
+        )
+    }
+
+    @Test
+    fun `a provider series' shift is read in its own zone`() {
+        val before = mapOf<String, Any?>(Tasks.DTSTART to at("2026-10-19T07:00:00Z"), Tasks.TZ to "Europe/Berlin", Tasks.IS_ALLDAY to 0L)
+        val after = before + (Tasks.DTSTART to at("2026-10-26T08:00:00Z"))
+        val shift = SubtaskReset.shiftOf(before, after, floating = ZoneOffset.UTC)!!
+        assertThat(shift.apply(at("2026-10-20T08:00:00Z"), isAllDay = false, timeZone = "Europe/Berlin")).isEqualTo(at("2026-10-27T09:00:00Z"))
+    }
+
+    @Test
+    fun `a provider series' rule set is read from its columns`() {
+        val state = mapOf<String, Any?>(
+            Tasks.DTSTART to at("2026-11-02T08:00:00Z"), Tasks.RRULE to "FREQ=WEEKLY", Tasks.EXDATE to null,
+            Tasks.IS_ALLDAY to 1L, Tasks.TZ to null,
+        )
+        val spec = SubtaskReset.specOf(state)!!
+        assertThat(spec.rrule).isEqualTo("FREQ=WEEKLY")
+        assertThat(spec.isAllDay).isTrue()
+        assertThat(SubtaskReset.specOf(state + (Tasks.RRULE to " "))!!.rrule).isNull()
+        assertThat(SubtaskReset.specOf(state + (Tasks.DTSTART to null))).isNull()
+    }
+
+    @Test
+    fun `the copy marker names the parent it was left under`() {
+        val json = SubtaskReset.copyMarkerJson("parent-\"1\"")
+        assertThat(SubtaskReset.markerParentFromJson(json)).isEqualTo("parent-\"1\"")
+        assertThat(SubtaskReset.markerParentFromJson(" [\"x-agendula-tick-copy\", \"p\"]")).isEqualTo("p")
+        assertThat(SubtaskReset.markerParentFromJson("[\"X-AGENDULA-TICK-COPYRIGHT\",\"p\"]")).isNull()
+        assertThat(SubtaskReset.markerParentFromJson(null)).isNull()
+        assertThat(SubtaskReset.markerParentFromResidue("X-OTHER:1\r\nX-AGENDULA-TICK-COPY:p\\,1")).isEqualTo("p,1")
+        assertThat(SubtaskReset.markerParentFromResidue("X-AGENDULA-TICK-COPY;X-P=1:p")).isEqualTo("p")
+        assertThat(SubtaskReset.markerParentFromResidue("X-AGENDULA-TICK-COPYRIGHT:p")).isNull()
+        assertThat(SubtaskReset.markerParentFromResidue(null)).isNull()
+    }
+
+    @Test
+    fun `a marked copy counts only under the parent it came from`() {
+        fun node(markerParent: String?, parentUid: String?) =
+            SubtaskReset.providerNode(2, null, null, emptySet(), markerParent = markerParent, parentUid = parentUid, state = done)
+        assertThat(node("routine", "routine").recurring).isTrue()
+        // Moved under another parent since: an ordinary completed sub-task there.
+        assertThat(node("routine", "other").recurring).isFalse()
+        assertThat(node(null, "routine").recurring).isFalse()
+        assertThat(node("routine", null).recurring).isFalse()
+    }
+
+    @Test
+    fun `a moved-on provider series resets with or without a copy, and its record is found by series and anchor`() {
+        val before = state(start) + (Tasks.RRULE to "FREQ=WEEKLY")
+        val after = state(start + week) + (Tasks.RRULE to "FREQ=WEEKLY")
+        assertThat(SubtaskReset.movedOn(before, after)).isTrue()
+        assertThat(SubtaskReset.movedOn(before, before)).isFalse()
+
+        val anchor = SubtaskReset.anchor(after)!!
+        val key = TickResets.key("org.dmfs.tasks", 4, anchor)
+        val record = SubtaskReset.encode(listOf(ResetSubtask(2, done)))
+        assertThat(key).isEqualTo("org.dmfs.tasks|4|${start + week}")
+        assertThat(TickResets.decode(TickResets.encode(1L, record))).isEqualTo(record)
+        assertThat(SubtaskReset.toRestore(SubtaskReset.decode(record)) { now(SubtaskState.FRESH) }.restore.map { it.id }).containsExactly(2L)
+    }
+
+    @Test
+    fun `a reset record expires with the tick horizon`() {
+        val now = 100L * 24 * 60 * 60 * 1000
+        val entries = mapOf(
+            "a|1|1" to TickResets.encode(now - 31L * 24 * 60 * 60 * 1000, "2,COMPLETED,,,,,,"),
+            "a|1|2" to TickResets.encode(now - 1, "3,COMPLETED,,,,,,"),
+            "garbage" to "x",
+        )
+        assertThat(TickResets.expire(entries, now)).containsExactly("a|1|1", "garbage")
+        assertThat(TickResets.decode("x")).isNull()
+    }
+
+    private val week = 7L * 24 * 60 * 60 * 1000
+    private val start = Instant.parse("2026-11-02T08:00:00Z").toEpochMilliseconds()
+
+    private fun state(dtstart: Long?, status: Int = TasksContract.STATUS_NEEDS_ACTION, exdate: String? = null, due: Long? = null) =
+        mapOf<String, Any?>(Tasks.DTSTART to dtstart, Tasks.DUE to due, Tasks.STATUS to status.toLong(), Tasks.EXDATE to exdate)
+
+    private fun spec(at: Long, rrule: String = "FREQ=WEEKLY") =
+        RecurrenceSpec(rrule = rrule, rdate = null, exdate = null, anchor = Instant.fromEpochMilliseconds(at), isAllDay = false, timeZone = "UTC")
+
+    @Test
+    fun `a provider series whose start moved later has moved on`() {
+        assertThat(SubtaskReset.movedOn(state(start), state(start + week), spec(start + week))).isTrue()
+        assertThat(SubtaskReset.movedOn(state(null, due = start), state(null, due = start + week), spec(start + week))).isTrue()
+    }
+
+    @Test
+    fun `ticking a later occurrence only adds an exception and moves nothing`() {
+        val after = state(start, exdate = "20261109T080000Z")
+        assertThat(SubtaskReset.movedOn(state(start), after, spec(start))).isFalse()
+    }
+
+    @Test
+    fun `a provider series ticked on its last occurrence is finished`() {
+        // OpenTasks deletes the master or drops its rule: there is no series state after.
+        assertThat(SubtaskReset.movedOn(state(start), null, null)).isFalse()
+        // Closed through its status.
+        assertThat(SubtaskReset.movedOn(state(start), state(start + week, TasksContract.STATUS_COMPLETED), spec(start + week))).isFalse()
+        // Dates moved, but the rule has nothing left from there.
+        val ended = spec(start + week, rrule = "FREQ=WEEKLY;UNTIL=20261103T080000Z")
+        assertThat(SubtaskReset.movedOn(state(start), state(start + week), ended)).isFalse()
+        assertThat(SubtaskReset.movedOn(state(start), state(start + week), null)).isFalse()
+    }
+
+    @Test
+    fun `a provider series moved earlier or without dates has not moved on`() {
+        assertThat(SubtaskReset.movedOn(state(start), state(start - week), spec(start - week))).isFalse()
+        assertThat(SubtaskReset.movedOn(state(null), state(null), spec(start))).isFalse()
+        assertThat(SubtaskReset.movedOn(null, state(start + week), spec(start + week))).isFalse()
+    }
+}

app/src/test/java/de/jeanlucmakiola/agendula/data/tasks/TickedCopiesTest.kt

@@ -0,0 +1,33 @@
+package de.jeanlucmakiola.agendula.data.tasks
+
+import com.google.common.truth.Truth.assertThat
+import org.junit.jupiter.api.Test
+
+class TickedCopiesTest {
+
+    private val now = 100L * 24 * 60 * 60 * 1000
+
+    private fun tick(copy: Long, daysAgo: Long) = Tick(copy, seriesId = 1, before = null, after = null, at = now - daysAgo * 24 * 60 * 60 * 1000)
+
+    @Test
+    fun `a tick past the horizon goes, and its copy stays known`() {
+        val ticks = mapOf(
+            "org.dmfs.tasks|1|10" to tick(copy = 7, daysAgo = 31),
+            "org.dmfs.tasks|1|20" to tick(copy = 8, daysAgo = 2),
+            "org.tasks.opentasks|5|10" to tick(copy = 9, daysAgo = 40),
+            "garbage" to null,
+        )
+
+        val (stale, known) = TickedCopies.expire(ticks, now)
+
+        assertThat(stale).containsExactly("org.dmfs.tasks|1|10", "org.tasks.opentasks|5|10", "garbage")
+        assertThat(known).containsExactly("org.dmfs.tasks", setOf(7L), "org.tasks.opentasks", setOf(9L))
+    }
+
+    @Test
+    fun `nothing expires inside the horizon`() {
+        val (stale, known) = TickedCopies.expire(mapOf("a|1|1" to tick(copy = 3, daysAgo = 29)), now)
+        assertThat(stale).isEmpty()
+        assertThat(known).isEmpty()
+    }
+}