Tap the first day of your most recent period, then pick how heavy the flow was.
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Tip: with a day focused, use the arrow keys to move and Enter to open the editor.
Your patterns
Everything here is computed from the days you logged. No averages borrowed from anyone else.
Cycle length history
Each bar is one completed cycle, in days.
Next three periods
Estimated from your own average cycle length. Estimates, not guarantees.
Cycle history
Periods are grouped automatically when logged days are adjacent or one day apart.
Most frequent symptoms
Counted across every logged day.
Settings
Defaults for predictions, plus everything you need to take your data with you.
Cycle defaults
Used only until you have logged enough periods to compute an average.
How many days a period usually lasts for you.
Days between ovulation and the next period. 14 is the usual estimate.
Only changes how the calendar is drawn.
Your data
Everything is stored in this browser only.
Days logged: 0
The backup is a plain JSON file with your logged days and settings. Keep it somewhere safe; it is the only copy that leaves this browser.
Remove data
Deletes every logged day and restores the default settings. Export a backup first if you might want it back.
Not sure where to start?
Load a sample history of five cycles to see predictions, the chart and the fertile window in action. Your current data is replaced, so export a backup first.
About Cycle Calendar
A menstrual calendar built to be quiet, private and predictable to use.
What it does
Log the days you bleed with a flow level, add symptoms, mood, a note and optionally your basal temperature. The calendar draws your logged periods, predicts the next ones from your own averages, and shades the estimated fertile window, ovulation day and PMS window.
Insights shows completed cycle lengths, your shortest and longest cycle, the variation between them, the next three predicted periods and the symptoms you log most often.
Privacy
Everything you enter stays in this browser's local storage on this device. There is no account, no server, no analytics, no advertising and no third party request at runtime. The app is a single HTML file that works offline once loaded.
The only way data leaves the browser is if you export a backup file yourself or print the summary. Clearing site data, or using a private window that you then close, removes everything.
How predictions work
The average cycle length is the mean distance between period starts, using your last six completed cycles. The average period length is the mean duration of your last six periods. If you have fewer than two cycles, the defaults from Settings are used instead.
Estimated ovulation is placed the luteal phase length before the predicted next period, and the fertile window covers the five days before it plus the day itself. Your logged days always win over any estimate.
Cycle Calendar is a personal tracking tool, not a contraceptive method and not a diagnosis. Cycles vary with stress, illness, travel and medication. Talk to a clinician about contraception, unusual bleeding, cycles shorter than 21 or longer than 35 days, or a period that stops for three months or more.
Built to last
Apache 2.0 licensed, no build framework, no dependencies at runtime, no cookies. The whole app is one HTML file plus a manifest and a service worker for offline use.
| Storage | This browser only (localStorage) |
|---|---|
| Network calls | None at runtime |
| Account | Not required, not possible |
| Languages | English, Romanian, Serbian (Latin and Cyrillic) |
| License | Apache 2.0 |