This Sunday sees that change from Autumn to the first day of Winter, and that means that we change from British Summer Time (BST) to Greenwich Mean Time (GMT).
GMT is measured from the "Meridian" line in London, a metal line which is a popular spot for tourists. It's the line from which all of the times in the world are measured.
Londeners might miss the clocks going back this year though because Bib Ben is going to be stopped this weekend whilst the engineers shange some of the hammers. (Well, the bells are being stopped, I'm not sure about the clock itself!)
So remember, on Sunday morning at 1am the clocks go back to midnight, Saturday!