It's that time of year again when the clocks change as autumn draws in.

In the UK, the clocks go forward in spring and back by one hour at 2am on the last Sunday in October.

This year, it's on Halloween on October 31, meaning we'll gain an extra hour of sleep.

While it may seem like a blessing as we gain more time in bed, a leading sleep expert has revealed how it can leave us feeling jet lagged up to a week later.

According to Loughborough University sleep expert Professor Kevin Morgan, changing the clocks in autumn and spring affects our circadian - or body clock - rhythm which can impact our wellbeing.

Most bodily functions are synchronised with the time of day and regulated by our ‘body clock’.

He said: “Clock times - from BST to GMT - change instantly, body clocks take longer to catch up."

Professor Morgan suggests that we experience a one-hour ‘social jet lag’ every time the clocks spring forward and fall back.

The clocks go back by one hour in October

In our bodies, it feels the same as the jet lag from a flight to Reykjavik for about a week after the clocks change. Relative to local time, we feel tired, hungry or wide-awake at the ‘wrong’ times.

Likewise, the spring clock changes are the equivalent to flying to Malta for a week or so afterwards.

Our circadian rhythm is closely linked to sleep. It responds to light during the day to keep us awake. At night it signals our body to produce melatonin (the sleep-promoting hormone) to help us sleep.

Research from CBD brand Love Hemp reveals why the extra hour in bed may be more trick than treat this Halloween.

It seems many Brits are pro-BST too, with59% of those surveyed saying they would prefer to stay on permanent summer time, preferring the lighter nights.

The period when the clocks are one hour ahead is called British Summer Time (BST), and when the clocks go back, the UK is on Greenwich Mean Time (GMT).

To help you remember, the clocks 'spring' forward for the transition to summer and the clocks 'fall' back.

Smartphones and other devices connected to the internet should automatically update, but don't forget to manually change any clocks or watches to the correct time.