At 2am this morning the majority of those living in the United States lost an hour's sleep. There was no earthquake; revolution did not break out in the streets; nor did fires erupt in the sky. In fact, most people were asleep at the time. What happened was the clocks moved forward silently by one hour to comply with a law requiring Daylight Savings Time (DST) to start on March 11.

For years, Americans had adjusted their clocks on the first Sunday in April but from now on we'll be making the switch on the second Sunday in March. The change is expected to have an economic benefit, since it's hoped that the longer daylight hours will lessen energy consumption.

Reminiscent of Y2k seven years before, there have been the techno-doomsayers who predicted the end of civilisation as we know it, with banks and brokers unable to process transactions, and hundreds of office workers turning up late for meetings. (Indeed, some thoughtful soul in my own company's IT department issued a memo with the suggestion that we should consider suspending meetings the first day back in the event we might miss them). If you were lucky, the cable company sent a signal that automatically re-timed your set top box. Users of PCs and Macs who had remembered to download the patch had no problems. I guess I'll find out on Monday morning if that 10am meeting is still on.

There was even advice for those seeking to beat the anticipated blues brought on by sleep deprivation (1).

There have been a few exceptions. DST - for the U.S. and its territories - is not observed in Hawaii, American Samoa, Guam, Puerto Rico, the Virgin Islands, and by most of Arizona (with the exception of the Navajo Indian Reservation in Arizona). These people have entrusted their fate to the natural rhythm of the heavens (2).

Saving daylight was first mentioned in 1784 by Benjamin Franklin in a humorous letter urging the people of Paris, France to save money by getting up earlier to use morning sunlight, thereby burning fewer candles in the evening (3). Franklin did not mention daylight saving time—he did not propose that clock time be changed. His letter was in the spirit of his earlier proverb

As is often the case in History, the motivation for change has its roots in something oddly human and mundane. In this instance think golf:

We have the US Congress to thank for this latest change. The Energy Policy Act of 2005 was passed by Congress and then signed into law by current President George W. Bush on August 8, 2005 (2). Under the new law, DST begins three weeks earlier than previously. DST is also extended by one week to the first Sunday in November. The new start and stop period begins March 2007. The original House bill would have added two full months, one in the spring and another in the fall. According to some U.S. senators, farmers complained that a two-month extension could adversely affect livestock, and airline officials said it would have complicated scheduling of international flights. So, a compromise was worked out to start DST on the second Sunday in March and end the first Sunday in November. Enactment of the Energy Policy Act of 2005 did not alter the rights of the states and territories to choose not to observe DST, which is how Arizona came to opt out. That's modern democracy in action, for you.

Back in the not-so-quite democratic days of Ancient Rome, the conscript fathers of the res Publica also grappled with the recalcitrant hours of the day and the ebb and flow of the seasons. Up until the fourth century BCE, the Roman day consisted of two parts, defined by the moment the sun past the meridian - the ante meridem and post meridiem which still survives in our own time keeping system. By the 300s BCE the day had been subdivided again by two into early and late mornings and afternoons. The introduction of the horologium, the sundial, brought with it the notion of hours. Unfortunately, the first sundial installed in Rome was calibrated for the path of the sun over a captured city in the island off the heel of Italy, not the city in Latium:

Later, the 'water clock' (horologium ex aqua or clepsydra) was developed and enabled the State to conduct its business come rain or shine. Just as our modern clocks have their buzzes and chimes and our public clocks their peal of bells, the horologia ex aqua, which Roman engineer and architect Vitruvius describes, were fitted with automatic floats which "struck the hour" by tossing pebbles or eggs into the air or by emitting warning whistles (4). Or the cry of a passer-by crying 'Duck!"

With the water clock, came the division of the day into twelve daylight segments and twelve nighttime parts. Yet for all that, the length of hours and days remained imprecise. Daylight is shorter in Winter, when night is long; and daylight endures longer in Summer while night is shorter. At the winter solstice (December 22), the day has only 8 hours 54 minutes of sunlight against a night of 15 hours 6 minutes. This means the day hour shrinks to 44 minutes while in compensation the night hour lengthens to 1 hour 15 minutes. At the summer solstice the position is exactly reversed; the night hour shrinks to its minimum while the day hour reaches its maximum.

As Jerome Carcopino points out, what this mean was Roman time was more fluid that our own. To say to a friend "I'll see you at the seventh hour" (1pm) would be an approximation at best.

Roman time was altogether more natural and self regulating, taking its rhythm from the celestial interplay of earth, sun and moon. In the end, our rush to regulate our modern lives and squeeze out every - first and last - photon of daylight, may prove futile. We are, after all, creations of Nature and She has her own time clock.

Jerome Carcopino, Daily Life in Ancient Rome, 1940