The decision to unify the onset of daylight saving in participating states could cause troubles for some newer mobile phones, according to Telstra.
Daylight saving will begin this weekend for NSW, Victoria, ACT, Tasmania and South Australia.
Most phones, PDAs and smartphones should update the time displayed automatically.
But according to a Telstra executive director, some newer mobile phones may have date/time software which overrides telecommunications providers' network settings.
Telstra advises mobile owners check to ensure their device is displaying the correct time on Sunday.