Clocks change 2015: When do the clocks go back and why?

Clocks in the UK will go back by one hour on Sunday 25 October, bringing an end to British Summer Time, or Daylight Saving Time.

The clocks change at 2am on the last Sunday of October, meaning there is less daylight in the evenings and more in the mornings. The period when the clocks are one hour ahead is called British Summer Time (BST), which happens on the last Sunday in March. There is more daylight in the evenings and less in the mornings, which is sometimes called Daylight Saving Time. When the clocks go back, the UK is on Greenwich Mean Time (GMT).

British Summer Time was first established by the Summer Time Act in 1916, after a campaign by a builder called William Willett. He was reportedly irritated with the "waste" of daylight in the early mornings of summer and suggested the change in 1907, publishing a pamphlet called The Waste of Daylight.

Should we change the clocks?

The debate about how we should set our clocks has been going on since standardised time was introduced with the expansion of the railways in the 1840s.

The New Zealander and astronomer George Vernon Hudson, an insect specialist, first proposed the modern idea of daylight saving in 1895. During his leisure time he collected insects, so favoured daylight hours when he could do so. He presented the idea of a two-hour daylight saving shift and presented it in a paper to the Wellington Philosophical Society.

Supporters of moving the clocks backwards and forwards argue that it saves energy, promotes outdoor leisure activity in the evening in summer, and is therefore good for physical and psychological health, reduces crime and is good for business.

Royal Society for the Prevention of Accidents has argued that lighter evenings would reduce the number of accidents. In 1968 and 1971, BST was employed all year round as an experiment. In October 1970, an analysis of road accident data published by HMSO (Her Majesty's Stationery Office) suggested there had been a substantial fall in the number of casualties in the evening. However, the period in which the research was taken coincided with the introduction of drink-driving legislation and the estimates were modified in 1989.

Opponents argue that the change is economically and socially disruptive. As conserving energy was originally one of the main reasons the clocks were pushed forward, studies have shown keeping BST is still beneficial. Research by the University of Cambridge in 2007 found an extra daily hour of sunlight in winter could save £485m each year as people are less reliant on electricity.

Moving the clocks permanently forward by an hour would also bring the UK in line with Central European Time, which means Britain would work during the same business hours as other European cities.