Zone — sleep debt & energy
Your energy is not random.
Most sleep apps show you what already happened. Zone forecasts what is coming — from the sleep pressure building in your brain and the body clock running underneath it.
How it works
Two systems, not a step count.
Human alertness is driven by two processes that have been measured for forty years. Zone models both, then subtracts one from the other. That is the whole trick — and it is why the forecast holds up without a wearable strapped to you.
Sleep pressure
A chemical debt that builds from the moment you wake and only clears while you sleep. Miss an hour and it carries into tomorrow.
Body clock
A 24-hour rhythm anchored to your temperature minimum. It does not care that you are tired — it lifts you in the evening whether you wanted that or not.
What you actually feel
Morning peak, afternoon dip, second wind, and the drop that follows. Not a mood — an arithmetic result.
Your day
Named to the minute, not to the afternoon.
Zone reads the turning points out of your own curve. Not “most people dip after lunch” — your dip, at the time it actually starts.
What you get
Your own history is never behind the paywall.
The loudest complaint in this category is apps holding your data hostage. Everything you log, and everything Zone works out from it, stays free. Pro buys the parts that take real modelling.
Zone
Free- Your energy curve for the next 24 hours, hour by hour
- Sleep debt, accumulated, decayed and paid down properly
- Tonight's sleep window, worked backwards from when you must be up
- Your chronotype and the phase markers that come with it
- A weekly report that grades the week and names one thing to change
- Backup and restore — a file you own, on a phone you choose
Zone Pro
Subscription- Smart wake window — an alarm time that lands between sleep cycles, worked out the night before so you can actually set it
- How your night was built — deep, REM and light cycle by cycle, so you can see why eight hours still felt wrong
- Live caffeine tracking — log what you drank, watch it decay, see how much is still circulating at lights-out
- Factor analysis — which habits measurably cost you sleep, tested against your own nights
- Jet lag planner — a shift schedule for the days before you fly
Servers, accounts and analytics SDKs. Zone has no backend — nothing you log leaves your phone unless you export it yourself. That is architecture, not a promise.
Languages, translated properly rather than machine-passed — English, Türkçe, Deutsch, Français, Español, Português, 日本語, 한국어.
Years of published chronobiology behind the model — Borbély's two processes and the Åkerstedt/Folkard inertia term, not a wellness heuristic.
Stop guessing at your own energy.
Log when you slept. Zone does the rest — and tells you what to do with every hour of what is coming.
Zone is a wellness tool, not a medical device. If you have persistent sleep problems, please talk to a doctor.