Terms of Use

1. Agreement

By downloading or using Zone you agree to these terms. If you do not agree, do not use the app. Zone is provided by Barış Yırtıncı, trading as yirtinci ("we", "us"). You must be at least 13 years old to use it.

2. What the app is

Zone models human alertness from published chronobiology — Borbély's two-process model and the Åkerstedt/Folkard three-process formulation — using the sleep you log. It produces a forecast, not a measurement.

A forecast is an estimate. It is built from a general model and your own entries, and it can be wrong — particularly if what you log is inaccurate, if you work shifts, travel across time zones, take medication that affects sleep, or have an undiagnosed sleep disorder. Do not rely on Zone for any decision where being wrong would be dangerous. It is your responsibility to judge whether you are fit to drive, operate machinery, or perform safety-critical work, and no output of this app changes that.

3. Your data

Everything you enter stays on your device. We do not hold it, cannot retrieve it, and cannot restore it for you. If you lose your phone without having exported a backup, that history is gone. Settings → Back up my data exists for exactly this reason, and using it is your responsibility. See the Privacy Policy for detail.

4. Zone Pro subscriptions

Zone is free to use. Zone Pro is an optional auto-renewing subscription that unlocks additional features. Prices are shown in the app in your local currency before you buy.

• Payment is charged to your App Store or Google Play account at confirmation of purchase.
• Renewal is automatic. A subscription renews unless it is cancelled at least 24 hours before the current period ends, and your account is charged for renewal within 24 hours of the end of that period.
• Cancelling is done in your store account settings — Apple: Settings → your name → Subscriptions; Google: Play Store → Payments & subscriptions. We cannot cancel a subscription on your behalf, because we do not hold it.
• Free trials, where offered, convert to a paid subscription unless cancelled at least 24 hours before the trial ends. Any unused portion of a trial is forfeited when a subscription is purchased.
• Refunds are handled by Apple and Google under their own policies. We cannot issue them.

Everything you log, and everything derived from it, remains available on the free tier. Ending a Pro subscription never removes access to your own history.

5. Acceptable use

You agree not to reverse-engineer, decompile, redistribute, resell, or attempt to circumvent the paid features of the app, except where such a restriction is prohibited by law.

6. Intellectual property

The app, its name, its interface and its underlying implementation belong to us. The scientific models it draws on are published research and belong to their authors. Your logged data belongs to you.

7. Availability and changes

We may update, change or discontinue the app or any feature at any time. Because the app runs entirely on your device, an existing install keeps working whether or not development continues.

8. Disclaimer and liability

The app is provided "as is", without warranties of any kind to the extent permitted by law. We do not warrant that its forecasts are accurate or that the app will be uninterrupted or error-free.

To the maximum extent permitted by law, our total liability arising out of your use of Zone is limited to the amount you paid us for it in the twelve months before the claim. Nothing in these terms limits liability for death or personal injury caused by negligence, for fraud, or for anything else that cannot lawfully be excluded — and if you are a consumer, your statutory rights are unaffected.

9. Governing law

These terms are governed by the laws of the Republic of Türkiye. If you are a consumer resident elsewhere, you keep the protection of any mandatory consumer law of your country of residence, and may bring proceedings in its courts.

10. Contact

[email protected]. We answer support mail ourselves.