Fix Date Format

Change-Id: I7065b56ffa86e99157b378958f0edbf2a338d31c
Fix the problem that a crash occured when repeat to show alarmclock settings dialog quickly in deskclock app

The original use of method addToBackStack is incorrect, the two steps in a fragment transaction should be executed as the order they defined.

Change-Id: I6dd5d947c6a589303b2c62dafd0ff78ff5072812