How to calculate cycle length from your period dates
Calculate menstrual cycle length from start dates, understand an average and choose manual or history-based predictions in Rythena.
Read the guideRYTHENA APP GUIDES
A clearer next step.
Practical app guides for period dates, small check-ins, privacy and partner sharing.
10 articles to explore
App guides
How to track your period without logging everything
Start a simple period journal in Rythena: save a start date, end the period when it finishes and add only the observations that matter to you.
Read the guideUsing an irregular period tracker when dates vary
Keep useful records of irregular periods in Rythena, understand withheld estimates and prepare clear dates for a healthcare conversation.
Read the guideOvulation calendar estimates: what the markers can tell you
Read an estimated ovulation marker and fertile-day window in Rythena, understand unavailable states and keep calendar estimates separate from confirmation.
Read the guidePeriod countdown: see the estimated date, not just a number
Understand days until your next period, a period-day counter and what to do when an estimated date passes in Rythena.
Read the guideA period mood tracker with room for your own words
Use Rythena's illustrated mood choices, frequent ordering and optional notes without assuming your cycle explains how you feel.
Read the guideUse a period symptom tracker for clearer, smaller records
Log symptoms with optional details, keep favorites close and prepare a free standard PDF with the upcoming Rythena app.
Read the guideA period tracker for couples, with sharing on your terms
Use Rythena Partner mode with private invitations, owner approval and separate sharing permissions. Viewing is free; owner publication requires Plus.
Read the guideMake a period tracking PDF report for an appointment
Prepare and review a free standard period-tracking PDF in Rythena, choose useful dates and keep control of what you share.
Read the guideWhat to look for in a private period tracker
Understand Rythena's local journal, optional encrypted backup, sharing controls and the difference between no-account tracking and online services.
Read the guideProduct instructions describe the upcoming iOS app. Our writing is AI-assisted and checked against the app implementation and linked sources; it is not clinically reviewed. How we write and correct content.