3PLUS Cruz Owner's Manual page 27

Preset Sleep:
You can also set a preset sleep schedule to program the
watch to automatically track your sleep during a specific
time frame.
Go to the 3Plus HYBRID App's menu, select settings, then
select "Preset Sleep".
In this setting screen, turn the "Auto Sleep" switch on and
adjust your "Bed time" and "Awake time" accordingly.
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