How does my UA Band know when I'm sleeping?
Your UA Band
automatically tracks your sleep based on your movement and the band’s angle on your wrist.
When your UA Band detects that you've been inactive and relatively still for more than 60 minutes, it will start to record the period as your sleep time. During sleep mode, your UA Band will track the quality of your sleep. When you get up from bed and resume activity, UA Band will recognize that you're awake and exit from sleep mode.