I am using a Google account on latest iOS, and the Calendar app appears to be adding it's own alerts to all-day events:
Click to enlarge images
Yes, I checked the "default alerts" in Settings:
Click to enlarge images
And even confirmed Google Calendar doesn't have the alerts:
Click to enlarge images
So… what gives? I've also tried deleting the entire Google account from my iPhone and re-adding it. No joy. It's driving me bonkers. Perhaps it's a bug with iOS 9.0.2, or something I'm just not understanding. Is anyone else having this issue/know a fix?
Best Answer
Do you use Apple Calendar on your Mac? (Preferences -> Alerts). Perhaps these are the preferences that push those alerts to your iPhone.