external
Open alpha
Circadia runs in any browser at circadia.owlandkestrel.com. Sign in with a free account, confirm your email, and your log syncs across your devices; Circadia Plus adds the full 14-night forecast.
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apphealth toolOpen alpha
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Health tool
Open alpha
Circadia
Public surface A sleep drift log for Non-24 rhythms, forecasts, and irregular rest patterns.
- Status:
- Open alpha
- Access:
- Free account; syncs once your email is confirmed
- Kind:
- Health tool
- Updated:
- October 26, 2026
Runnable state
What Circadia Does
Log
Log a night in one tap
Tap Sleep Now when you lie down and Wake Now when you get up, or fill in the Log form after the fact. A night broken into pieces is kept as one split sleep, so the gaps don't skew your numbers.
Drift
Your drift and your τ
Circadia estimates your body's own day length, τ, from your real nights, and shows how far your sleep moves each day, with a confidence range on the estimate.
Forecast
Smart and Adaptive forecasts
Two models forecast your next sleep windows from your own history. Free accounts see one night from each model; Circadia Plus unlocks the full 14-night forecast.
Clock
The Clock dial
A 24-hour dial with a ring for each day, so drift shows as your sleep stepping around the clock. The outer planner ring places meds, meals and wind-down at times counted from when you wake.
Calendar
Calendar and actogram
The drift calendar shows every night day by day, with an Awake view of the hours in between. The actogram stacks your nights so the staircase of a drifting rhythm is plain to see.
Analysis
Analysis
Totals and trips around the clock for each year, how steady your drift is, which tags and flags show up most, sleep by menstrual-cycle phase, and how close each forecast came to your real nights.
Import
Bring your history
Import years of past nights from Apple Health, Fitbit, Sleep as Android, AutoSleep, Garmin (through a Guava export) or a spreadsheet, and Circadia works out your rhythm from all of it.
Event Check
Will I be awake?
Enter an appointment and Event Check tells you whether you're likely to be awake, what time it will feel like to your body, and which windows that week will be easier.
Report
A report for your doctor
A print-ready report with your chart, actogram and key numbers, plus a plain-language section on Non-24 and other circadian rhythm disorders. Save it as a PDF to bring to appointments.
Community
Community and Sky
See people whose body clocks run near yours, vote in polls, and find your own star in Sky, which shows where your body clock sits among everyone else's.
Games
Daily games
Inference, Synapse and Tessera each have a daily puzzle that resets when your body's day ends, not at midnight, with leaderboards to play against.
Research
Research, with consent
Sharing is off until you choose a level: with Circadia, with researchers, or in published research. You can turn it off any time, though data already in a published dataset stays there.
Journal updates
Jun 14Dayah Dover
One Month of Open Alpha
One month into open alpha, Circadia has moved from a tool I built for my own impossible sleep into an app with enough real N24 data to make the research side feel less theoretical. The Community tab is live, Jon replaced the particle filter forecast with a tag-aware Kalman-IMM model, and the app now has enough users to expose the administrative layer under health software: platform rules, security audits, server costs, and the boring financial reality of keeping something useful alive.
Read May 30Dayah DoverWhat Is Non-24-Hour Sleep-Wake Disorder?
A plain-language guide to Non-24-Hour Sleep-Wake Disorder (N24): what it is, what "free-running" means, why sighted people get it too, how it's diagnosed and managed, and why several of its stranger features are completely normal for the disorder: marathon wake periods, sleep debt that won't clear, a sleep window that slams shut.
Read May 27Dayah DoverTwo τ Changes Today, and the Bug I Caught On My Own Data
Why your τ tile might look a little different from this morning — and why the change is mostly the math finally admitting it can't fit a 30-hour cycle onto a 24-hour clock face.
Read May 26Dayah DoverOne Number Is Never the Whole Story
Why Circadia lets you change the math behind your sleep — and why my own settings look nothing like the defaults. Featuring a very bad Airbnb, a fourteen-hour lurch, and the embarrassing number of hours I do not spend asleep.
Read May 25Dayah DoverWhy I'm Asking You to Tap One More Button
I went down a rabbit hole this week about how to share your data with actual researchers without doing something stupid. Here's what I learned, what I built because of it, and a small ask at the end.
Read May 25Jon MeriwetherYour Sleep Forecast Shouldn't Panic After One Weird Night
Circadia's new adaptive forecast is better at handling skipped nights, naps, crashes, recovery sleep, and sudden changes in your sleep pattern. It learns only from sleep data people choose to share — and the more of your own history you share, the better chance Circadia has of understanding your pattern.
Read May 15Dayah DoverTwo Days of Circadia Open Alpha
None of the apps I tried even let me manually enter my sleep data, let alone predict my next bedtime or track my drift. So I built one. Two days into open alpha, here's what's been built, what's coming, and a real ask.
Read May 17Jon MeriwetherWhat Happens When You Share Sleep Data With Circadia
Shared sleep data does not disappear into a mysterious AI pile. It helps us replay history, grade forecasts, tune the recipe, and keep only changes that make Circadia more trustworthy and useful.
Read