A number of iOS users have found that their calendar alarms seem to have stopped working today. This issue has caused a few to wonder if any alarms would work, but Apple Spokesperson Natalie Harrison mentioned to MacWorld that the problem is expected to resolve itself on Monday.
The specific issue only affects nonrecurring alarms, so people can just enable the alarm as a recurring event for it to work as expected. The problem is expected to only be for the first couple of days in January, and alarms set on Monday or later should be functioning properly.
Do not expect Apple to address this problem with an update, unless the issue is found to persist for upcoming years (though in that case Apple would have plenty of time to implement fixes in scheduled iOS updates). This issue will affect iPod Touch, iPad, and iPhone users.