Circadian timing is about when you sleep, wake and get light.
daygauge shows your sleep against your usual window, along with time in daylight from Apple Health, so you can see when your timing drifts.
Start with what your own data can show.
Circadian advice is often generic: get morning light, avoid late light, sleep consistently.
daygauge makes it personal by showing when you slept, how that compares with your usual window and whether the drift repeats.
daygauge shows your sleep timing against your usual window. It also shows time in daylight from Apple Health, and the places on your Timeline.
What this guide covers.
How the app handles this.
What this can look like in the app.
Time in daylight: 18 minutes before 10:00 on 4 of 7 days.
ExampleA pattern is only called proven after it repeats on your own paired days. Missing readings lower confidence.
Try one small change, log it in Quick Log, then compare your next readings.
Example 1
Evening timing: you logged late caffeine twice, and your wake time was later on those days.
Example 2
Timing drift: your sleep window started 42 minutes later than your usual.
Further reading.
These studies describe groups of people. They help explain the topic, but they cannot tell you what will happen to you.
- npj Biological Timing and Sleep 2025 review of light and the circadian clock
- Journal of Nursing Management 2025 trial of LED light therapy in shift-work nurses
- eLife 2023 UK Biobank sleep regularity and mortality study
Research context only. daygauge does not diagnose, treat, prevent or predict disease risk. Personal medical concerns belong with a qualified clinician.
What daygauge does not do.
Related guides.
Want to see your own sleep timing against your usual window?
daygauge is free to download. Pro is £8.99 a month or £49.99 a year.
Download on the App StorePersonal analytics, not medical advice