As many people know, Apple has a bug in their iPhone that prevented alarms from going off at 1st and 2nd of January 2011. What is strange is how that bug might happen - i.e., as far as I know this bug happens in all timezones and nobody is switching off DST on Jan 1st, so it's not timezone or DST-related. Also, Jan 1st seems to be nothing special as a UNIX timestamp, so something like sign change or integer overflow can't be the reason. It is highly improbably that alarm code has something like if(date == JANUARY_1_2011 || date == JANUARY_2_2011) turn_alarms_off(); - that would be a sabotage and not a bug. So the question is - could you imagine and describe a bug that would cause the alarm to fail exactly at Jan 1st and 2nd everywhere while letting it work otherwise, without specifically referring to those exact dates?

Of course, if somebody knows the real cause, that would be a definite answer, but if nobody knows it - I think it is interesting to think what might be the cause of such strange bug.