We noted the importance of checking the time on devices when daylight saving began over the weekend in many states, but it turns out that iPhones running iOS 4 have a more subtle problem: recurring alarms go off at the wrong time once daylight saving has kicked in.
Numerous reports on Twitter and discussion forums attest to the problem, which first became evident last week in New Zealand, where the switch daylight saving happens a week ahead of Australia). The issue purely applies to recurring alarms (such setting an alarm for the same time every day to wake you up for work). The effect varies depending on when the alarm was created, according to one poster on Apple's own support forums:
Recurring alarms that were set prior to the Daylight Saving switch went off an hour later than intended. Recurring alarms that have been set since Daylight Saving began, go off one hour earlier than the time they are set for.
Even users in states where daylight saving doesn't apply have reported problems, so anyone using an iOS 4 device needs to be cautious. (Reports suggest there's no issues with the older iPhone 3 releases unless they've been upgraded.)
Until Apple issues a patch, the easiest way to avoid the problem appears to be setting individual one-off alarms, rather than recurring ones. Problems with daylight saving are hardly unknown, but let's hope Apple does a better job of managing it in future.