Problem:

Most of the time, the first meeting of the day or the day starts around a specific time - let’s say 8:30am.  Therefore, you may wake up by the same time in order to make that.

However, sometimes an appointment may be scheduled earlier than normal - say 2am for an international call, or 7am.  These occurrences are rare, and one may forget to wake up early for them.

Two Solutions

A) Within the sleep workflow - preferred option

When one sets an alarm on their phone for the next day, the alarm could show concurrently on screen if there are any calendar items prior to / near the selected time.  

This would trigger the user as they set the sleep timer to choose another time.

This is the preferred option as the notification about an earlier appointment occurs concurrently in the workflow of setting an alarm - therefore removing the possibility of setting the wrong time.

B) Push notification

Receiving a typical push notification 15 minutes prior to a calendar item is not much use when one’s phone is in mute mode asleep.

It would be more helpful if my phone knew the average time that I wake up / or the average time my meetings start in the morning.  I could set this time once manually. Or a very straightforward algorithm could look at my calendar and figure this out.

If the device notices that an appointment is scheduled the next day earlier than average, it could send a push notification the night prior reminding the user of this.