Microsoft Band can optionally monitor the quality and duration of your sleep overnight, providing a surprisingly detailed range of sleep data, including how long it took you to fall asleep, the total amount of time you were asleep, how much time you spent in restful sleep and light sleep, your resting heart rate while you slept, and graphs of your sleep pattern and heart rate over the duration of that sleep.
Note: This tip is based on content in my free e-book, Microsoft Band Field Guide, which I'm currently writing. You can always find the latest version of this book—which will be updated as Microsoft Band is updated—at the Field Guide Books web site.
To monitor your sleep, tap the Sleep tile on your Band. Then, press the action button. While you sleep, Band will monitor the quality and duration of that sleep, and it will keep its display off. In the morning when you wake up, press the action button and then tap the Yes button when prompted.
You can always see a few details about your most recent sleep on your Band. From the Sleep tile, swipe to the left to see the date you last slept, the amount of time you slept, your sleep efficiency (as a percentage, where higher is better), the number of times you woke up, and the amount of calories you burned while sleeping.
You can also access your most recent sleep from the Sleep tile in the home view of the Microsoft Health app (on Android, iPhone or Windows Phone). But thanks to the additional onscreen real estate, this view of that provides a lot more information.
To see a history of your sleep, navigate to your activity history in the Microsoft Health app. (Menu, then Activity History.) To view only sleep, tap the Filter button (next to Metric) and then choose Sleep.