Why do we change the clocks?

Various reasons have been given for changing the clocks and it's not, as some people thought many years ago, in order to save candles. I think the best reason for advancing the clocks in March is so that during the summer months we can enjoy the longer hours of daylight, but now we are at the end of October so we have to change them back again. I alter my clocks before I go to bed on the Saturday evening. It takes me a little while to do them all as I have to get out the instructions for some of the things. Usually I change everything except the telephone. I always forget the telephone. When everything else is done, then I have to change me.