Last weekend we had witnessed yet another alarm clock bug in IOS (All devices running 4.2.1 were affected). On 1st and 2nd of January, single non-repeated alarms did not sound, as a result many iPhone owners were late for work, school, date, etc. Similar problem was reported after daylight saving time change last autumn, but it affected only repeated alarm events.
There is no official statement from Apple yet, but rumours say there will be no patch for this bug, moreover the problem should correct itself on the 3rd of January.
EDIT: Both repeated and one time alarms already work fine on 3rd of January (iPhone 3G running iOS 4.2.1)
Note to self: buy a simple alarm clock, and never be surprised again.