CUPERTINO, Calif. (AP) - Many iPhone customers had some explaining to do after they overslept to start the new year, due to a glitch in the gadget's alarm clock feature.

Users who set their iPhone alarm for a single wake-up rather than recurring use found the alarm didn't go off with the year's arrival, Apple Inc. spokeswoman Natalie Harrison said Sunday.

A fix is in the works, and all iPhone alarms will work properly starting Monday, she said.

The glitch affects iPhones using Apple's latest iOS 4.0 operating system, including earlier versions of the smart phone whose users have downloaded the latest software.

It wasn't immediately clear what caused the alarm problem, or how many iPhone users were affected. Online postings on blogs and social media sites described people being late for work, church services and other appointments on Saturday and Sunday because of the problem.

The problem is the second in two months involving iPhone's alarm clock. The company said in early November that the end of daylight savings time could cause problems for iPhone users. In that instance, Apple said that repeating alarms set on iPhones and some versions of the iPod touch might not recognize the Nov. 7 end of daylight savings time, and might work incorrectly shortly before or after the time change.

The Cupertino-based company introduced the iPhone in 2007. Apple sold 14.1 million iPhones in its fiscal fourth quarter, from July through September.

(Copyright 2011 by The Associated Press. All Rights Reserved.)