Some users have reported an issue in which the iPhone’s clock function does not work properly, with a grey screen appearing when the user attempts to access the alarm or other functions. Additionally, the Clock application may unexpectedly quit, returning the user to the home screen.
There are two potential fixes for this issue:
Change International settings Navigate to Settings>General>Region format and change the region, then re–attempt use of the clock application.
Restore the iPhone Press the Restore button in iTunes while the iPhone is connected to your computer.