Fix "all day" event reporting on lockscreen

Sometimes, all day events from the next day took precedence over scheduled
events from that day's night, because the all day event times are given in
UTC, versus local time for the scheduled events. This patch corrects this
incorrect behaviour by converting UTC times to local times and then
comparing events to find the nearest one.

Change-Id: I5f7f73c52e6c1935460c5ab2255008dfd701f279