Store all day events w/ UTC timezone

* All day events are supposed to be stored w/ UTC as the time zone
* We already zero out hour, minute, and day
* Use DTEND for non-recurring and DURATION for recurring all day events

Bug: 2440161
Change-Id: I31f2e5a355b721c06b4022b57ccc8a29b288a5d9
1 file changed