Apple iPhone users have suffered from a problem with non-repeating alarms in 2011. Users with iOS4 have reported that one-off alarms haven’t worked on 1st and 2nd January, although Apple says all alarms will work properly again from 3rd January.
Repeating alarms weren’t affected, making this the opposite of a problem that occurred at the end of summer time.
[Sources: Macworld.com; 9to5mac.com]