Jean-Luc Makiola
7e7079df00
Review follow-up on the midnight alarm. The month widget could still show the wrong month after the rollover, and by way of the exact workaround #228's reporter described. ShiftMonthAction stored an absolute index on every tap, so paging forward and back — which looks like a no-op and was how people forced a redraw — silently pinned the widget to the month that was current at the time. It kept redrawing correctly and kept drawing August into September, today's circle nowhere on the grid. Landing back on the current month now clears the key instead of writing it, so the widget goes back to following the date. Paging somewhere else and staying there is left alone; that one is a choice, and the today button undoes it. The alarm also had no way back once something dropped it without telling us — a force-stop, a battery-restricted transition, an OEM freeze — short of the user opening the app. onUpdate is the one wake-up the system still owns through updatePeriodMillis, so both receivers re-arm from it. That doubles as a window narrower: setAndAllowWhileIdle's delivery slack scales with how far out the alarm was set, so re-arming every half hour keeps midnight's window at minutes rather than hours. Boot and package-replace now re-arm and stop there. The host sends APPWIDGET_UPDATE after both, so the redraw was a second pair of wide provider reads and RemoteViews serialisations in a cold process, exactly when the device is busiest. Smaller things: the unreachable lookahead fallback armed 5 seconds out, which would have been a wake-loop rather than the late redraw the comment claimed — an hour now. The action guard's comment was copied from ReminderScheduleReceiver along with its claim that the broadcasts are protected; PROVIDER_CHANGED is not, and the real reason the guard is worth having is that the receiver must stay exported. Application start does its sync off the main thread now. Tests moved onto frozen historical transitions — Berlin 2024 both ways, Havana 2018 — since the 2026 dates they used depend on DST rules that can still change under a tzdata bump. The Berlin "fall back" case never repeated midnight, so it now says what it actually checks (a 25-hour day must not overshoot) and a real repeated-midnight zone, pre-2019 Sao Paulo, pins the known limitation instead of implying it is handled. Dropped the two assertions that restated the code, and added the one that was missing: that the receiver's action guard admits the action the alarm is sent with, which is the single point where the whole thing would fail silently.
Calendula
A modern Material 3 Expressive calendar for Android.
Reads, writes, and reminds — on top of the system calendar, with zero network access.
Calendula is named after the flower whose name — like the word calendar —
comes from the Latin kalendae, the first day of the month. It lives
entirely on top of Android's CalendarContract: any calendar synced to your
device (CalDAV via DAVx5, Google, local, WebCal subscriptions, …) simply
appears, and everything you create or edit syncs back the same way. No own
database, no sync stack reinvented.
✨ Features
Calendar
- Month, week, and day views with a one-tap view switcher
- Full event details — attendees and their responses, reminders, recurrence (humanized), availability, visibility, foreign time zones
- Per-calendar visibility toggle, grouped by account
Editing
- Create, edit, and delete events — including recurring events with scoped writes: only this event, this and all following, or the whole series
- Recurrence picker with one-tap presets and custom rules (interval, weekday toggles, end conditions); rules it can't express are preserved verbatim
- Conflict-safe saves: if an event changed elsewhere while you were editing, Calendula asks instead of silently overwriting
- Read-only calendars (WebCal, birthdays) are detected and respected
Reminders
- Event reminders delivered by Calendula itself as notifications — essential when it's your only calendar app, since Android delegates reminder delivery to calendar apps
- Tap a reminder to land on the event
Design & privacy
- Real Material 3 Expressive throughout — dynamic color (Android 12+), expressive motion and shapes, light/dark theme
- English and German UI plus community translations (Spanish, French, Italian, Polish, and more in progress), per-app language setting — and open to more languages
- Zero telemetry, zero analytics, no internet permission — your data never leaves the device
📦 Install
Pick whichever channel you already use — they all install the same app:
| Channel | Updates | Notes |
|---|---|---|
| Official F-Droid | On F-Droid's build schedule | Recommended; no extra setup |
| Self-hosted F-Droid repo | Minutes after a release | Fastest; needs the repo added once |
| Codeberg release / Obtainium | Per release | Plain APK download, or automated by Obtainium |
| Google Play | Per release | Signed with Google's key — see below |
| Build from source | Whenever you build | Full control |
F-Droid (recommended)
Calendula is on the official F-Droid repository — just search for Calendula in any F-Droid client, or install it from f-droid.org.
F-Droid rebuilds from source on its own schedule, so a new version usually shows up there a few days after release.
Self-hosted F-Droid repo (fastest updates)
Every release is built, signed, and published to a self-hosted F-Droid repository as part of the release pipeline, so it lands there first. Add it once and your F-Droid client handles updates from then on:
-
In your F-Droid client, open Settings → Repositories → Add (or open the link below on your phone):
https://apps.dev.jeanlucmakiola.de/dev/fdroid/repo?fingerprint=C2C0640402BF458FC0ED957AF0B37AA4C14022E72F89CE90B5965B458CF73425Repo:
https://apps.dev.jeanlucmakiola.de/dev/fdroid/repo· fingerprint (SHA-256):C2C0 6404 02BF 458F C0ED 957A F0B3 7AA4 C140 22E7 2F89 CE90 B596 5B45 8CF7 3425 -
Refresh, search for Calendula, install.
Codeberg release / Obtainium
If you'd rather not use F-Droid at all, every release is also published on
Codeberg with the
signed APK (calendula_vX.Y.Z.apk) and a .sha256 checksum attached — download
and install it directly.
For automatic updates from that channel, use
Obtainium — on the phone,
add Calendula in one tap,
or do it by hand: Add App → paste https://codeberg.org/jlmakiola/calendula
→ Add. Either way, Obtainium tracks the releases and prompts you when a new
one appears.
Google Play
Calendula is live on Google Play: play.google.com/store/apps/details?id=de.jeanlucmakiola.calendula.
Play builds are signed with Google's key rather than mine, so switching between Play and any other channel requires an uninstall (and with it, a fresh start for app settings — your events live in the system calendar and are unaffected).
Build from source
The build is a plain Gradle build with no proprietary dependencies — see
docs/BUILDING.md (note the floret-kit submodule).
Official F-Droid, the self-hosted repo, and the Codeberg releases all share the same signing key, so you can switch freely between them without reinstalling. Google Play is the exception — see above.
📚 Documentation
- Contributing — how to report, propose, and patch
- Building from source — requirements and Gradle tasks
- Architecture — the layered design and key pipelines
- Milestones — what's shipped and what's next
🤝 Contributing
Bug reports, ideas, and patches are all welcome on Codeberg.
The short version: start with an issue. Features get a yes-or-no before they
get code, and both features and bugs are assigned a milestone whose
release/vX.Y.Z branch your pull request then targets. Typo and docs fixes can
skip straight to a pull request. Translations don't go through pull requests at
all — Weblate owns them.
Read CONTRIBUTING.md before writing code: it covers the
workflow, the build (note the floret-kit submodule), and the architectural
rules a change is reviewed against.
🌍 Translations
Calendula ships in English and German, with community translations in Arabic, Chinese, French, Italian, Polish, Portuguese, Russian, and Spanish at varying degrees of completeness — partial is fine, untranslated strings simply fall back to English. You're warmly invited to add or finish your language. Translations are managed on a self-hosted Weblate:
No coding needed — register on the Weblate server, pick (or request) a language, and translate the strings in your browser. You can also reach this link in the app from the top of Settings → App language.
📜 License
MIT — Jean-Luc Makiola, 2026