“Periodical” is a calendar to calculate the fertile days according to Knaus-Ogino. One motivation was to create an application which does not have any “gimmick” – no flowers or other decorations, as seen on other calendars of this kind, but reduced to the essential functionality.


WARNING: It is not recommended to use this calendar to avoid pregnancy! There are more accurate methods, like measuring the basal body temperature.

It is possible to backup all data to a memory card or “internal” memory, if present.

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.


Source (Github)

Download as APK

Download at Google Play Store

Download at F-Droid

Or scan the following QR Code for the download via the Google Play Store:

Periodical on Google Play

Version history


Feature: Updated French translation.


Feature: Added Japanese translation.


Feature: Added AppCompat for older devices.


Feature: Added option to change luteal phase length.

Bugfix: Fixed wrong sort order in list view.

Feature: Improved permission handling for Android 6 or later.


Bugfix: Fixed handling of backups in newer Android versions.


Feature: Added translations for Czech and Dutch (thanks to the Github user „Pander“) ergänzt.

Feature: Adjusted color scheme to Material Design.


Feature: Added Russian translation.

Bugfix: Added some missing content descriptions for some week day labels.


Feature: Improved accessibility support: All elements now provide a meaningful content description, so the app can also be completely with TalkBack.


Bugfix: Details list in right sort order again.


Feature: Added Spanish translation (thanks to Laura Arjona Reina).

Feature: Extended the color scheme to display days before the first cycle and after the last calculated cycle.

Feature: Code cleanup and optimization.

Feature: Target platform changed to SDK version 20 (Android 4.4).


Bugfix: Fixed wrong weekday labels when changing the start of the week.


Feature: Added Italian translation (thanks to Valerio Bozzola).

Feature: Additional preference for start of the week (sunday or monday).


Bugfix: Fixed a problem with restoring databases and preferences.


Bugfix: Under Android 2 there was a crash when you tried to open the newly introduced preferences.

Feature: The French translation has been updated.


Feature: Added preferences to adjust the default length of a period in days.

Feature: “About” and “Help” are now separate activities displaying HTML and no dialog boxes any longer.

Note to developers: Beginning with version 0.15 Eclipse is not used any longer. The project now uses IntelliJ IDEA Community Edition.


Feature: Modified color scheme to display future fertile days a bit lighter.

Feature: The calculation of the longest and shortest period is now done for the last 12 entries only to avoid the fertile period getting longer but never shorter again.

Feature: The “today” marker is now a circle and not an oval any longer.


Feature: French translation updated.

Feature: Increased resolution of overlay icons for MDPI devices.

Feature: There is now a separate layout for landscape view.


Feature: The calendar is now a bit “nicer” with rounded corners, nicer “today” marker and symbols
for the first day of the period and the day of ovulation.


Feature: The day of ovulation is now being calculated and displayed in the calendar.


Feature: Added new app icons for low and high density display devices (ldpi, hdpi, xhdpi).

Feature: Detail list now allows to select an entry to display the corresponding month.

Feature: Reworked color display and focused elements in the calendar are now displayed properly.

Feature: Modified manifest so the app and its data may be backed up using ADB.

Bugix: Database cursor was not closed properly when loading the detail list.


Feature: Added new dialog to display help text.

Feature: Added GPL text to “about” dialog.

Feature: Changed color scheme from red, green, white to red, blue, yellow according to the chain of Maria Hengstberger.

Feature: Modified layout to display text in calendar view more readable.

Feature: Updated french translation.


Feature: Added French as additional language.

Bugfix: Text correction.


Feature: Better support for newer Android versions (Action Bar, adjusted layout) and improvements in the UI.

Feature: The detailed list now also shows period lengths.

Bugfix: The longest period is now correctly displayed if it is shorter than 28 days.


Bugfix: The database cursor was not closed properly after reading the data.


Bugfix: The identification of the current day in the calendar was not updated if Periodical was in the background and activated again on the next day.

Feature: An individual application icon was added.


First release.