26th October: British Summer Time Ends.

If you live in the UK and haven't already done so you need to put your clocks back an hour. When you've done that you can read the 10 facts about time zones:

1. Greenwich Mean Time (GMT) as a worldwide standard was first established in 1884 - but only 22 of the world's nations actually voted for it. Only 25 were even asked. France and Brazil abstained and the Dominican Republic voted against.
2. It was several years before GMT was used all over Britain. Before that people used solar time wherever they were, which would vary by a few minutes. When people started travelling long distances by train there needed to be some sort of agreement about what time the train was going to leave or arrive, so it was the railway companies which first officially adopted it in 1847. It was legally adopted in 1880.
3. Why is it called "mean" time? Because even at the Greenwich Meridian the time of the highest point of the sun can vary by up to 16 minutes from day to day, so the mean time is the average time of the highest point of the sun.
4. Although Greenwich is in England, England only uses Greenwich Mean Time for less than half the year, between the last Sunday in October and the last Sunday in March. Most of the time we're on British Summer Time (BST).
5. The only country to use GMT all year round is Iceland.
6. A way to remember which way you need to alter your clocks: Spring forward, fall back.
7. Most places which change their clocks do so by a full hour. There is an island off Australia, Lord Howe Island, which changes its clocks by half an hour so that in winter it is ten and a half hours ahead of GMT. Places near the equator where the amount of daylight doesn't vary much, don't bother.
8. Larger countries like the USA have several time zones, except for China, which decided to adopt one time zone throughout the land. This means that the sun is at its highest at 11am in the east and at 3pm in the west of China - and in some parts of China the sun doesn't rise until 10am.
9. The idea of British Summer Time was first suggested in 1908 by William Willett who noticed that most people were still in bed when he went out riding in the early morning and it was a waste of daylight. The idea wasn't taken on until 1916, a year after he died.
10. Back then, putting the clocks back would be even more of a pain than it is now. Clocks in those days were designed to only move forwards, and trying to move the hands backwards would break them - so the only way to do it was to move the hands forward by 11 hours.