In the United Kingdom the clocks change twice a year, the clocks come on the last Sunday in March and the last Sunday in October.
When they return, we have an extra hour in bed.
The clocks will go back one hour at 2 am on Sunday, October 28, 2018.
Britain will switch from British Summer Time (BST), which means more daylight at night and less in the morning, to Greenwich Mean Time (GMT) which means less daylight at night.
To remember when watches change, there is a simple phrase to remind you.
This is "spring forward, fall", so the clocks advance in the spring and return in the fall (fall).
Why do clocks change?
The idea was first suggested by the American inventor Benjamin Franklin, who came up with the first idea in Paris in 1784.
He said that if people got up earlier when it was lighter, they would save candles.
However, builder William Willett, the great-great-grandfather of Chris Martin of Coldplay, brought the idea to the UK and argued that if the clocks went ahead in the summer, it would save on energy costs and give people more time to enjoy the outdoors .
In 1907, he published a pamphlet called The Waste of Daylight, which encouraged people to get out of bed earlier.
He was an enthusiastic golfer and crossed when his games were shortened because the sun was setting and there was not enough light to continue playing.
The idea of changing the clocks was discussed by the government in 1908, but it did not become law.
But the British government finally introduced it in 1916, a year after Willett's death.
The British government passed the Daylight Saving Act and summer time was introduced to save fuel during the war and the money.
There was an experiment between 1968 and 1971 that kept the clocks one hour ahead of GMT throughout the year.
But Britain returned to the GMT family system in winter and British summer time between March and October.
When do clocks change in 2019?
In 2019, the clocks will advance on March 31 at 1 am, when the country returns to British Summer Time (BST), which means less light in the morning and more at night.
They will return one hour at 2 am on October 27, 2019 and return to GMT.
The reason why clocks change on a weekend in the middle of the night is to limit the disruption of schools and businesses.