How to use Alarms & Clock app
Dismissing or snoozing alarms
When an alarm goes off, you’ll hear a sound and see a notification that you can snooze or dismiss.
It appears even if the app is closed, sound is muted, or your PC is locked. You can even dismiss alarms from the lock screen without unlocking it. However, in most cases, alarms won’t sound if your PC is asleep, and never when it’s shut down.