A menstrual calender with calculation of fertile days according to Knaus-Ogino.
About this app
This application calculates the fertile days according to Knaus-Ogino and can track menstrual symptoms.
WARNING: It is not recommended to use this calendar to avoid pregnancy! There are more accurate methods, like measuring the basal body temperature.
The data can be backed up on a memory card or "internal" memory, if present.
If you have any further questions or want to help me with translations in other languages, please contact me via e-mail - thank you.
This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
You can obtain the source on my website.
Licensed under GPL-3.0-or-later.
What's New in v1.96
Imported from the F-Droid repository index.
Version history
Apr 20, 2026 · 2.8 MB · Android API 21–36 · code 109
Imported from the F-Droid repository index.
SHA-256 9db2ccf1758f09de924ffcdf231f5fb6745d66daf7dd21aa50946cdff301a5fb
Nov 22, 2025 · 3 MB · Android API 21–36 · code 108
Imported from the F-Droid repository index.
- A cycle can start without change of the average calculation.
- Orta hesablama dəyişmədən bir dövr başlaya bilər.
- Cyklus může začít beze změny ve výpočtu průměru.
- Ein Zyklus kann beginnen, ohne dass sich die Durchschnittsberechnung ändert.
- Un ciclo puede comenzar sin modificar el cálculo del promedio.
- Un cycle peut démarrer sans modification du calcul de la moyenne.
SHA-256 9b8279e2a2a4c69aba6047f6ae524660491b56389dec41fe33926c71a37a8690
Nov 17, 2025 · 3 MB · Android API 21–36 · code 107
Imported from the F-Droid repository index.
- A cycle can start without change of the average calculation.
- Orta hesablama dəyişmədən bir dövr başlaya bilər.
- Cyklus může začít beze změny ve výpočtu průměru.
- Ein Zyklus kann beginnen, ohne dass sich die Durchschnittsberechnung ändert.
- Un ciclo puede comenzar sin modificar el cálculo del promedio.
- Un cycle peut démarrer sans modification du calcul de la moyenne.
SHA-256 3f77ab30d394dbe5d500507ecdf4f6236a93123812b799759e2b00fe848d4495
Will it run on your device?
78%
- Runs on a broad range of modern Android versions.
- ABI coverage is focused on newer 64-bit devices.
- Aligned with the latest Android target SDK expectations.
Installation Guide
Open Settings on your Android device
Go to Security → Unknown sources (or Install unknown apps)
Enable "Allow from this source" for your browser or file manager
Open the downloaded APK file from your Downloads folder
Tap "Install" and wait for installation to complete
Launch the app from your home screen
Make sure to re-enable Unknown Sources restrictions after installation for security.
How to install this safely
How to verify the file you downloaded
Before you install anything, confirm the file is the one described here. On a computer, run shasum -a 256 your-download.apk (macOS or Linux) or certutil -hashfile your-download.apk SHA256 (Windows), then compare the output character-for-character with the SHA-256 on this page. If a single character differs, the file is not the build we recorded — delete it.
What the signing certificate proves
Every Android app is signed with a private key that only its developer holds. The fingerprint on this page is a hash of the matching public certificate, and it proves continuity rather than identity: it tells you a build came from whoever signed the earlier ones. Android enforces this at install time — if a package claiming to be de.arnowelzel.android.periodical is signed with a different key, the system will refuse to install it over your existing copy. A fingerprint that changes between releases is worth pausing on, because a repackaged app that has been modified by someone else cannot keep the original signature.
How to roll back to an earlier version
If the current release misbehaves, 1.95 is the last build before it. Android will not install an older version code over a newer one, so you must uninstall Periodical first — which clears its local data unless you have a backup. Reinstall the older APK only if its signing fingerprint matches the build you already trust, and check the API range: an older release may target an Android version your device has moved past.
Why we list sources instead of hosting everything
The official store channel is almost always the right choice: it updates automatically and carries the publisher's own distribution guarantees. A direct APK is useful when a device has no store access, when a rollout has not reached your region, or when you need a specific version — and only when the publisher has authorized that copy. APKBrowse does not list pirated, cracked, or unauthorized rebuilds of Periodical, and a listing is removed when the evidence for it stops holding up.
Get Periodical
Every source we list for de.arnowelzel.android.periodical is legality-reviewed. Pirated or cracked builds are never offered.
Other sources
F-Droid listing
officialF-Droid builds this app from source and signs it. This is its official listing, with older builds and full release notes.
Source code
verified publisherThe upstream repository this build is compiled from.
We check legality and signature continuity, but device behaviour still varies. Install at your own discretion.
App Information
Security Verification
We record provenance; we do not run malware scans. Verify the hash yourself before installing.
SHA-256 Hash
9db2ccf1758f09de924ffcdf231f5fb6745d66daf7dd21aa50946cdff301a5fb
Signing certificate
ef16ef5fee58b3f0964fdd693270524a7855134eb53c13d02065ffc876dbaf01
Permissions Required
Previous Versions
The signing certificate fingerprint for this release is on record, so a build that does not match it did not come from this publisher.
Report a problem with this listing
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