Millions of Australians will lose an hour of sleep in a few weeks’ time as daylight saving comes into effect.

All but three states and territories will wind their clocks forward by an hour on the first weekend in October.

Here’s everything you need to know before daylight saving time starts.

Why does daylight saving exist?

The whole purpose of daylight saving is to make better use of natural daylight and reduce energy consumption depending on the time of year.

During the warmer months, this means moving the clocks forward to enjoy more sun in the evenings.

In the cooler months, the clocks are moved back so Aussies can make the most of morning light.

Why doesn’t all of Australia have daylight saving?

Not all Australian states and territories observe daylight saving.

In contrast to Queensland, Western Australia, and the Northern Territory, the states of New South Wales, Victoria, South Australia, Tasmania, along with the Australian Capital Territory, adjust their clocks twice annually.

The main reason for this is that Queensland, WA, and the NT are situated closer to the equator, meaning the variability in daylight hours across the seasons is not as significant in these areas.