If you live in the United States, you're probably already aware that the nation is set to switch to Standard Time on November 7, moving clocks one hour back. What you may not be aware of is that if you're using an iPhone or other iOS device as your primary alarm clock, it might not make the switch as planned -- and you could end up late to work on Monday as a result.
iOS 4 introduced a bug into how iOS devices handle the switch between Daylight Saving and Standard Time. The bug got some attention when it first hit New Zealand back in September -- when our clocks rolled forward an hour, our iOS alarms did not. Many New Zealanders woke up an hour early following the switch to DST because of this bug, myself included. The same thing happened a couple weeks later when certain Australian territories switched to DST, and Apple promised a fix.
Southern Hemisphere iOS users had it bad enough being woken up an hour early, but when Europe switched to Standard Time last week, iOS users there found their alarms going off an hour late. The internet was flooded with reports of Europeans whose iPhones and iPods failed to wake them up on time last Monday. At the same time, some of our US commenters noted that alarms in the States were going off an hour early.
Apple has posted a support doc on its iOS DST issues, and the company recommends changing repeating iOS alarms in the Clock app to single-use alarms instead as a way of skirting the issue. This procedure worked for us in New Zealand, but it has the added inconvenience of having to remember to set the alarm every day.
Bottom line: if you're worried about being late to work on Monday, or losing an hour of sleep, the best advice we can give you is to use a different alarm other than your iPhone or iPod touch for now. While the issue is reportedly resolved in the forthcoming iOS 4.2 update, that update is unlikely to be publicly released before the changeover to Standard Time this Sunday -- so if you're on thin ice at work already, don't depend on your iPhone to wake you up on Monday morning.