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The changing of the clocks, which will give us 60 minutes more of Sunday to enjoy, has been going on since 1981 in compliance with a EU Directive affecting all countries in the European Union. But the adoption of different times for Winter and Summer started much longer ago. All this moving clock hands about is not for nothing. It's done with the aim of saving energy. The first people to realize the benefits of changing the clocks and put the idea into effect were the British and the Irish, who in 1916 invented British Summer Time so as not to waste coal by using so much electric light. Spain and France joined in three years later. After World War II, Summer Time disappeared but the oil crisis of 1973 made a lot of countries, including Spain, start to bring back the measure in order to stretch the hours of sunlight during the Summer months.

In December of last year the European Union passed the Ninth Directive, which for the first time talks about an indefinite period for the measure because �the correct functioning of some sectors not only transport and communications, but also other branches of industry require a stable long term programme�. The new Directive preserves the starting and finishing dates for Summer time; the last Sunday in March we put the clocks forward an hour, and the last Sunday in October we put them back.

According to estimates from the Institute for Diversification and Energy Saving (IDAE), during the months when Summer time has been applied more than 11,000 million pesetas have been saved in this country, 10,000 in lighting in homes and another 1,000 in air conditioning in commercial premises and services, which represents a saving of 5% and 3%, respectively. If the average annual consumption of a Spanish family is 3,200 kWh, the saving will be more than 1,000 pesetas in every home. A sum of money not to be sneezed at but which, according to ecologists, is a drop in the ocean compared with the amount of energy wasted in Spain.

But the changing of the clocks isn't everyone's cup of tea: some people are against it because they consider it unnatural. In 1997, France, one of the pioneers of this measure, argued that changing the clocks alters people's personality and is bad for the health of children and old people because it upsets their meal times, sleep patterns, etc. There are even experts who consider that it can be harmful for agriculture and livestock since the animals, to a far greater extent than us, are sensitive to the light conditions of the different seasons. Psychiatry suspects, although there is no hard evidence for this, that changing the clocks especially affects night people and those suffering from depression. Most psychologists however consider this to be a passing inconvenience and the fact that the clocks change in the early hours of the morning helps to lessen the effects.

• November 1, 1884, the International Meridian Conference in Washington (United States) agreed on the current time zones. The Earth was split into 24 equal parts from pole to pole and the reference time (Greenwich Mean Time) was established at the Royal Observatory at Greenwich (United Kingdom). 12 standard meridians , of 15� each, lie to the east and another 12 to the West of this line, while the Greenwich meridian is considered as meridian 0.
• The idea of applying Summer time appeared for the first time in an essay written by Benjamin Franklin in 1784 when he was ambassador of the United States in France. He suggested to the French that they put the clocks forward an hour in the Summer to make better use of daylight, and so cut back on the use of candles worth several million francs.
• Nearly 80 countries in the world change their clocks to save energy.