Tonight we turn our clocks back one hour. One night next spring we will move them ahead again. And so we continue, year after year, to perform a ritual that doesn't do much harm or much good and clearly doesn't make much sense: the ritual of Daylight Saving Time.

The Daylight Saving Time idea started in wartime. It was a conservation measure, a response to dwindling national resources. Factories and offices could reduce electric lighting needs if daylight hours fit working hours better. This fit is accomplished instantly and easily by resetting the clock. Here is the idea:

The traditional working day runs from 9 a.m. to 5 p.m. It begins four hours before 1 p.m. It ends four hours after 1 p.m. The business day centers around 1 p.m.

But the hours of daylight center around 12 noon. By ancient tradition noon means mid-day. It divides daylight. For the ancients, artificial light was scarce. Their noon divided both the business of the day and the light of day. We moderns work into the night and sleep late in the morning. So the middle of the business day has slipped back. It now comes an hour after the middle of daylight. Our business mid- day comes at 1 p.m. The middle of daylight is at 12.

Many felt conscience-bound to rectify this iniquity. If the business day centers on the sunshine day we get greater use of the light of day. We'll need less and so use less artificial lighting, argued many a senator.

It may well be worthwhile to center the business day so as to maximize the benefit of daylight. The clock, then, should be kept set for this benefit. It should be fixed on Daylight Saving Time. Why ever shift the clock back to the off-center business day? Why go back to light-wasting Standard Time during part of the year?

The answer for some is a matter of life style. They find it unappealing to have darkness in the morning. Standard Time makes winter mornings lighter at the normal clock waking hour. "It pushes darkness into nightime where it belongs," say some among us. And, indeed, there are more dark standard hours at day's end. There are fewer dark ones at day's start. The Standard Time off-center business day originally evolved to permit sleeping late. Daylight Saving time eliminates this achievement.

More important: people respect tradition. Many of us have humility before nature's complexity. We are loathe to tamper with nature's division of daylight merely to suit the changing fashion in business hours. Reasoned one senator, "They won't like the government tampering with the clock. Time is sacred." So he suggested a compromise. "We'll adjust the clock, but only during part of the year." The senator cemented patriotism to tradition in the normal political manner. For patriotism we have half a year of Daylight Saving Time. For tradition we have half in Standard Time.

But our clock resetting dates are at the wrong time of year. There are only two short intervals during the year when Daylight Saving Time actually does save daylight relative to Standard Time. And for one of these we use the wrong clock setting.

There is no saving in mid-summer. In summer the daylight hours far exceed the business day--adjusted or not. Sunrise comes before the business day begins. The sun sets after the business day ends. No daylight is saved because, with either clock setting, business hours are daylight ones; no artificial light is needed.

In mid-winter too, Daylight Saving time has no daylight saving advantage over Standard Time. The hour difference between the two determines merely which hours will require electricity--not their number. For example, four of the eight normal business working hours may require electric lighting in mid-winter. On Standard Time these four are different from the four arising under Daylight Saving Time. But since, in either case, there are four dark hours, neither setting has a savings advantage.

Only during two short periods of the year does Daylight Saving Time actually reduce work place energy consumption. These occur between the seasons of summer and winter. Daylight Saving Time reduces business- day electric lighting needs in very late fall, around October, and in very early spring--in February and March.

But in February and March the nation is on Standard Time, not Daylight. Thus in one of the two short periods during the year when Daylight Saving Time is efficacious we don't even use it!

Can a ritual be less rewarding? Few participants take pleasure in it. It's a burden to people who schedule travel and transportation. And it does not accomplish the small good for which it was introduced. It does not even fully save daylight.