Just a period tracker. Pay once. Yours forever.
One job, done beautifully. Pay once — no subscription, no nags. Your data stays on your phone.
On the App Store and Google Play soon.
Period apps grew subscriptions — then grew quizzes, articles, and streaks to pay for them.
All of it wrapped around what used to be a dot on a calendar — and all of it sitting on someone else’s server, holding the most sensitive health data a person has. The tool stopped working for the person using it.
Pay once. Own it forever.
One payment, then it’s yours. No recurring revenue means no reason to manufacture engagement — nothing to nag you back, nothing to upsell. Like the calendar on the wall: bought once, not rented.
A gem is something you own, not something you rent.
Your data stays yours.
Everything you log lives on your device. There’s no Peridot account and no Peridot server, so your data never reaches us. Export a CSV copy whenever you want one.
This is the whole app.
A calendar, a countdown, and a button to log. Logged days are solid; the days ahead are an estimate. No feed, no quizzes, no streaks to keep. You consult it for a few seconds, and then it leaves you alone.
Scroll the months — the dot is the whole idea. Then tap Log period and watch a guess become a fact.
A single most-likely day, and an honest window around it.
Peridot gives you one most-likely day plus a window that tightens as it learns you — never an oracle, never a fertility guarantee. The days it’s sure of are solid. The days it’s guessing are dashed, so the difference is never just a color.
Three flat steps of one green, deepest at the most-likely day. Predicted days are dashed; logged days are solid. No blend ever connects a fact to a guess.
The architecture is the argument.
Privacy here isn’t a promise we ask you to trust. It’s a consequence of how the app is built.
