From my personal blog:
This weekend, I was traveling out of state. While away, my phone started alarming at 4:00am. Which is very strange because I hadn’t set any alarm for that hour, nor is there any event scheduled for that time.
After a bit of investigation, I discovered that it was because an event later that day (a simple reminder, scheduled for 9:00am) accidentally had its alert time set to “Time to Leave”:
In case you’re unaware, the “Time to Leave” alert is a feature meant to let you know when you need to start traveling in order to arrive at the location for the event. For instance, if you have a doctor’s appointment, and the doctor’s office is 15 minutes away from home, it will alert you 15 minutes before the appointment when you’re home. But if you happen to be somewhere else, it will alert you based on the estimated travel time from your actual location (based on a computed route, traffic conditions, etc.)
You can probably figure out what happened. My reminder was scheduled for 9:00am, with a location set to my home. And the alert time was “Time to Leave”. So when I was out of state (a 5 hour drive away from home), it dutifully alerted me 5 hours before the reminder’s time - at 4:00am.
Let this be a friendly reminder to double-check your alert settings when creating events, especially if they are daily/weekly reminders.