In one sentence
The things you remember about the night, logged as timed events: getting into bed, a toilet trip, a stretch of lying awake, and being up for the day.
Why it matters
A device records the night from the outside and misses the one thing you know for certain: when you were awake. Wearables see lying still as sleep, so they underestimate time awake by 12 to 48 minutes and overstate efficiency, and the moment you fell asleep is better known to you than to your wrist (see Time to fall asleep). The Night Log is the sleep diary the research field uses, cut down to four events. The Consensus Sleep Diary, the standard instrument the specification draws on, asks the same questions on paper every morning; VT asks them in the app, with a clock.
What goes in it
Into bed (a time). A toilet trip or a stretch of lying awake (a start time, and an end when you know it; if you only know roughly when you got back to sleep, VT marks the end as estimated). Up for the day (a time). Nothing else, and nothing is compulsory: a night with no entries is read from the device alone.
How to log it well
In the moment, with one tap: the app has a night mode for it, so that nothing has to be remembered. Entries made in the morning are accepted too, and marked as made afterward; log them before you look at the device's chart, so that the chart does not edit your recollection. Log the toilet trip even when the device shows you asleep through it, which is the point.
How Vitality Tracker uses it
In the morning VT draws your entries over the device's chart, so you can see which wakings it caught and which it slept through, and an "up for the day" well after the device's record ends flags the night as possibly cut short. At launch the entries do not change the sleep scores. The Night Log does not feed Symptom Radar or Capacity.
How far to trust the number
Self-reported, which for wake inside the night is the better instrument, and for total sleep the worse one: people who sleep badly tend to under-count their sleep, so VT takes the events from you and the sleep from the device.
Sources
- Vitality Tracker Sleep Scoring Methodology, open specification v2.0.1, public edition (§7.2, the three calibration tiers, which name the Consensus Sleep Diary as the diary instrument).
- Carney CE, Buysse DJ, Ancoli-Israel S, et al. The Consensus Sleep Diary: standardizing prospective sleep self-monitoring. Sleep 2012;35:287–302 (cited in VT's science article on optimal sleep). doi:10.5281/zenodo.23223863
- Vitality Tracker, What VT measures (catalogue of 15 October 2026).