Privacy
Short version: the dates you enter never leave your device.
The calculators
- Every calculation happens in your browser. The dates you enter are never sent to us or anyone else.
- Your dates aren’t put in the page address, saved in your browser or written to any log.
- When you close or reload the page, what you entered is gone.
- “Add to calendar” builds the file on your device. We never see it.
What we don’t use
- No cookies.
- No advertising and no third-party tracking scripts.
- No accounts, no sign-up and no email collection.
What our host sees
- Like any website, our hosting provider (Vercel) receives standard request information when you load a page, such as your IP address, browser type and the page you asked for. It is used to deliver the site and protect it from abuse. It never includes anything you type into a calculator.
- We use Vercel Web Analytics to count page views. It uses no cookies and doesn’t identify you: it records which page was viewed, the referring site, your country and your device type. It never sees anything you type into a calculator.
- Fonts are served from this site, not from a third party.
Contact
- Questions about privacy? Email hello@koyomia.app.
Not medical advice
- Koyomia shows estimates based on the dates you enter. It isn’t medical advice and it isn’t birth control. If something feels off, talk to a doctor.
Last updated 16 November 2026