After several failures, I sat down and figured out how to reliably use the alarm.
The phone must be ON or ASLEEP, but not shut off, for the alarm to work. The alarm still works if you press the Power button to turn off the display or if you’re running other apps.
The alarm sounds for 1 minute, then automatically goes to snooze mode.
While ringing, there are two ways to “dismiss” the alarm, so it still goes off tomorrow.
1 Tap the Dismiss button, if on screen.
2 Press a physical side button, such as camera or volume, if this alarm clock option is set.
While ringing, don’t press Home! If pressed accidentally, the only way to dismiss the alarm is to:
1 Unlock the phone.
2 Swipe down notifications.
3 Tap the alarm notification
4 Tap Dismiss.
In snooze mode, you can see the next alarm time on the phone’s lock screen and the clock screen. Also, the snooze alarm appears in the notifications drop down screen.
In snooze mode, the only way to dismiss the alarm, before it goes off again, is to:
1 Swipe down the notifications screen (*).
2 Tap the alarm notification.
(*) Note that sometimes the notifications screen won’t open. For example, if the clock app is running and you press the power button to turn off the screen. Here’s what to do:
1 Press the Home or Back button.
2 Unlock the phone.
3 Swipe down notifications.