What counts as a night, and naps

What counts as a night#

The night window#

One rule decides which sleep is "the night" and which is a nap, for every device and for the MyBodyAI phone app:

• The night of a date is sleep that reaches into the window from 21:00 to 09:00 on your clock.
• A nap is sleep wholly between 09:00 and 21:00. It is kept separately.
• A date with no sleep in the window keeps its daytime sleep as the night, so a person who works nights is not charged a sleep debt for the sleep they had.

The night is filed under the day you wake up. The label above the gauge reads "Night 3 → 4/11" for the night from the evening of 3 November to the morning of 4 November, followed by the clock times of the night and "this morning" or "yesterday morning". When the night shown is not the last one, the label carries a chip "older data, last recorded night".

How long a night may be#

Exact calculationHow long a night may be

A sleep length under 30 minutes or over 16 hours is not accepted as the length of a night: the first is a nap or a sensor bounce, the second is not a believable record. Up to 16 hours counts, so a long sleep after a night awake is not thrown away. Sleep Debt counts at most 12 hours of one night. A day's naps are stored up to 12 hours.

Which device's night#

Exact calculationHow we pick one device's night

When two connected devices both report the same night, we keep one of them. If the one we keep holds less than 60% of your usual night and another device's staged night of the same date holds at least 75% of it, we take the other, the one nearest your usual night: a short record from one device should not outrank a full night measured by another. Two readings from one device that arrive through two routes are the same night and are never swapped, and a night without stages never replaces one that has them. More on how devices combine is in several devices at once.

An unusual night#

A night that is far off your usual is still counted: you may really have been awake. It earns a notice at the top of the Sleep tab:

• Much shorter: under 60% of your usual night. "The night to 3/11 is much shorter than usual: 2 h 40 min of sleep against your usual 7 h 05 min."
• Much longer: more than 3 hours over your usual. A watch left on at the bedside can file hours of "sleep" that you did not have.

Your usual night here is the middle value (median) of your measured nights over the last 365 days, and needs at least 3 nights of at most 12 hours each.

The notice says "It is counted as it was measured." and offers choices:

• "Use the night from [device] (7 h 20 min)", shown only when another device measured that date;
• "Delete this night": the night is taken out of the day and your scores leave it out; the notice then reads "The night to 3/11 is deleted; your scores leave it out.";
• "Undo", which puts the night back as it was.

The cross closes the notice. It stays closed per night and per state, on every device you use. Deleting a night does not change the data at your device.

A night that arrives late, or not at all#

Nights reach us late as a matter of routine, because a watch writes the night when it next syncs with the phone. Until it arrives:

• Scores for the day are worked out on your usual night (the median of your own last 7 nights) and the day is marked provisional, so a delivery delay does not look like a bad night. It applies only to today and yesterday, only when a whole night is missing, and only for values the device delivered on at least 4 of the last 7 days. When the real night comes in, the day is scored again. Details in Body Status.
• The Sleep tab does not show the stand-in night. It shows your latest recorded night with the chip "older data, last recorded night" and the days since, so you never read an invented night as a measurement.
• When there is evidence of no sleep. If your device recorded the day (steps, stress or heart rate) but no sleep, we classify the night. Only a measured sign that no restorative sleep happened counts as one (the Body Battery recharge under 40% of your usual recharge, with no climb of the battery between the evening and the morning). Then the tab says "Last night's sleep was not recorded" and "No overnight recovery was detected. Below is your last recorded night, not today." With no such evidence the night is flagged but never punished: "Showing your last recorded night below, not today."
• A night that was recorded but short. Under 90% of your need is a short night, under 55% of the need or under 4 hours a very short one. The need used for this is never taken below 6h 40m, so a night under 6 hours is always short. The consequences for Body Status and readiness are in the night rule.

Naps#

A nap is daytime sleep that your device records as its own record, wholly between 09:00 and 21:00. It is not part of the night: the length, stages and efficiency of the night stay the night's. What a nap does:

• It appears on the card "Naps" ("Šlofíky"): the total time, how many naps, the average length and a strip of the last days. The card hides itself when the night or period on screen has no nap.
• It counts toward the day's sleep need in Sleep Debt, up to 2 hours a day, and not on a day when the naps are longer than the night (that is a split sleep period, not a nap). See naps in Sleep Debt.
• It can matter for the cap on the device's score: a night that is short of your need only by an amount a credited nap covers is not treated as short.

When two devices record daytime sleep on the same day, the larger figure stands rather than the sum.

Frequently asked questions#

Why does it say my night was much shorter than usual?#

Because the night was under 60% of your usual (the median of your nights over the last year) or because a watch filed a sleep period too short to be the whole night. If another device of yours measured that date, the notice offers its night. If you really slept little, leave it: the night is counted as measured. If the watch was lying on the table, delete the night and the scores leave it out.

Does a nap raise my Sleep Quality?#

Not by its own length or stages: a nap is not part of the night. It matters in one place: a night short of your need only by what a credited nap covers is not treated as short, so the cap on your device's score does not apply. It counts toward the day's sleep need in Sleep Debt, up to 2 hours a day (naps).

Why does my Sleep tab show an older night, and my day is marked provisional?#

A watch writes the night when it next syncs with the phone, so nights reach us late as a matter of routine. Until the night arrives, the scores for the day are worked out on your usual night (the median of your last 7 nights) and the day is marked provisional. The Sleep tab shows your latest recorded night with the chip "older data, last recorded night", never an invented one, and when the real night comes in the day is scored again. See A night that arrives late, or not at all.

I work nights. Is my daytime sleep counted?#

The night of a date is sleep that reaches into the window from 21:00 to 09:00, and a nap is sleep wholly between 09:00 and 21:00. A date with no sleep in the window keeps its daytime sleep as the night, so a person who works nights is not charged a sleep debt for the sleep they had. See The night window.