Normally, clocks are put forward an hour on the last Sunday in March, and then put back an hour on the last Sunday in October.
In 2016, summer time will last from 27 March to 30 October.
During that time, we move our clocks forward by an hour - so, if you normally get up at 8am, it will feel like 7am.
The change is called 'daylight saving', and the idea is to make the most of natural daylight, by arranging for the hours of the day when we do the most things to happen when it's light.
Starting the day earlier means that mornings are darker, but it stays light for longer in the evenings.
It was first done in the UK in 1916 - 100 years ago - during the First World War.
The aim was to save fuel, and give people more time to work in the fields.
Now, some people think that we should have British Summer Time all year round.
At 1am on Easter Sunday, the clocks moved forward by one hour, marking the start of British Summer Time.