Cycle Diary: Period Tracker

Cycle Diary is a simple, private period and cycle tracker. Log your period, symptoms and mood, and see clear estimates for your next period and cycle phase — without an account, without sync, and without your health data ever leaving your phone.

Everything stays on your device
There is no account, no login and no server. Nothing you log is ever uploaded anywhere. Export your data to a file whenever you want a backup, and delete everything permanently at any time from Settings.

Clear, honest estimates
Once you've logged a couple of cycles, Cycle Diary shows your estimated next period, cycle phase and (optionally) a fertile-window estimate. Every prediction is clearly labelled "Estimate" and drawn differently from logged days on the calendar, so you always know what's actually recorded versus what's a guess.

Log what matters to you
Track flow level, symptoms and mood alongside free-text notes, and see cycle-length trends and symptom frequency in Insights.

Built for privacy on a shared phone
Optional app lock (PIN or biometric) and a "hide in recents" toggle keep your log private even if someone else picks up your phone. Reminder notifications never show cycle details on the lock screen.

Cycle Diary shows estimates calculated from the information you enter. It is not a medical device, does not provide medical advice, and must not be used as a method of contraception or to diagnose, treat or prevent any condition. Cycle length varies, and estimates can be wrong. For any health concern, consult a qualified healthcare professional.

Recent changes:
First public release of Cycle Diary: private period tracking with calendar, symptoms, mood and notes, cycle estimates and insights, reminders and optional PIN lock.