The rationale behind daylight-saving time is to make better use of daylight. Not only does it give more time for leisure activities, the theory is that it saves energy by cutting the need for electric lights and other uses of electricity.

Demand for electricity for lighting homes has been shown to be directly related to the times when people go to bed at night and get up in the morning. In the average home, 25 percent of electricity is used for lighting and such things as TVs and stereos.

People also tend to plan more outdoor activities that take them away from home. They not only cut electricity because they are not home to turn on lights and TV sets, but also enjoy the extra hours of daylight in recreational activities.

Studies done by the Department of Transportation show that daylight-saving time does indeed trim the country's electricity usage by a small, but significant, amount — a total of about one percent each day.

In addition, several studies in the United States and Great Britain have found that DST shift cuts traffic accidents and fatalities by close to one percent. True, there are more accidents in the mornings, but that is offset by the decrease in evening accidents.

Around the world

Approximately 70 countries use some form of daylight-saving time — or Summer Time, as it is called in some places. India and Japan are major industrialized countries that do not shift the clock in the summer. China, which adopted a single time zone in 1980, did observe DST from 1986 to 1991 but doesn't do it now.

Most countries situated on the equator also don't observe DST since daylight and evening hours are similar all year round, and there is no advantage in changing the clock.

Not every one likes it

DST has both fans and critics. Among the reasons cited by those who don't like it are:

• The hassles of changing clocks and adjusting to a new sleep schedule.

• If you live in a warm climate, you might be spending more to cool your home during summer evenings, thus offsetting energy savings.

• More daylight may mean more use of automobiles, and thus more consumption of gasoline.

• If your work is tied to sunrise (such as it is for farmers), you still have to "go to work with the chickens."

• Getting children to go to sleep when it's still light outside can be hard.

• Children often have to go to school in the dark.

• It's not nice to mess around with Mother Nature — or your internal time clock.