Residents in the ACT, NSW, Victoria, South Australia and Tasmania will lose an hour of sleep on Sunday, October 4, when they have to turn their clock forward by one hour.

The changeover officially happens at 2am on Sunday morning.

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Moving clocks forward means it will immediately become 3am at that time.

If you have somewhere to be on Sunday morning, it's a good idea to make sure you're aware of the changes and your smartphone or alarm clock has the correct Daylight Saving Time.

Daylight saving will last from October 4 through to April 4 next year, when clocks will have to be turned back by one hour and residents will notch an extra hour in bed.

Queensland, Western Australia and the Northern Territory do not participate in daylight saving.

Most smartphone devices and computers adjust the time automatically, but analogue clocks need to be changed manually.