The bells weren't ringing for many iPhone users this New Year's weekend, when thanks to a glitch the alarms on Apple's iconic mobile phones failed to go off, causing many to oversleep.

It was the second time in just a few months that the alarm function on the phone failed to activate correctly, prompting an avalanche of complaints on the social networking micro-blog Twitter.

"Dear iPhone, why didn't your alarm go off this morning? I set six of them. I've now missed church. Thanks for nothing," said one user Sunday morning.

"Some sort of digital iPhone pandemic is going on. Alarm clock failure reports are pouring in from all sources around the globe," said another Twitter user.

Apple said in a message sent to Macworld magazine that the California-based company was aware of the problem. "We're aware of an issue related to non-repeating alarms set for January 1 or 2," spokeswoman Natalie Harrison said.

"Customers can set recurring alarms for those dates and all alarms will work properly beginning January 3."