MOBILE phone and computer time settings have been thrown into chaos by the extension of daylight saving in the east – and the confusion is set to continue with the country now divided into four time zones.

Phones, computer programs and even Telstra's speaking clock service reverted to standard time a week too early in some eastern states yesterday, after the end of daylight savings was extended to 3am on April 6.

But someone didn't tell the phones, some of which had a mind of their own.

Telstra spokesman Peter Taylor said new-generation mobile phones and BlackBerry handsets were affected most because they had software that could override their systems.

"Technology and time went haywire at 2am yesterday, so many people slept in... Thankfully, it was a Sunday," Mr Taylor said.

Some computers and electronic clocks also switched back to standard time too early, and some companies have issued software updates for Microsoft Outlook to correct premature changes to its meeting calendar service.

Western Australia reverted to standard time yesterday, while NSW, the ACT, Victoria, South Australia and Tasmania are still in daylight saving time.

Queensland, which has refused to adopt daylight saving, is an hour behind the other eastern states and the Northern Territory is an hour and a half behind.

In the US last year a similar change in daylight saving schedules meant hundreds of millions were spent on adjusting computer systems.

Although the east coast may be affected, the problem shouldn't affect Western Australia, which is in the middle of a three-year trial of daylight saving, because its systems are already in place.

Premier Alan Carpenter has conceded, while personally not a fan of daylight saving, that it does benefits the state, particularly the business sector.

WA has rejected daylight saving at several referendums and the three-year trial is an attempt to end the debate.