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	—	Coming soon
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:

1. 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=C2C0640402BF458FC0ED957AF0B37AA4C14022E72F89CE90B5965B458CF73425
   

   _{Repo: 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}

2. 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 (coming soon)

Calendula is on its way to Google Play as an additional channel. It isn't live yet — this section gets a link once it is. Play builds will be signed with Google's key rather than mine, so switching between Play and any other channel will require an uninstall.

Testers wanted. Play requires a round of closed testing before the app can go public, and I'm still looking for testers. If you'd like to help, email business@jeanlucmakiola.de with the Google account address you want to use — that address is what I need to add you to the closed test.

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.}

📚 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:

→ Help translate Calendula

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