On the last Sunday in October — October 29 in 2000 — we dutifully turn our clocks back an hour to what we know as Standard Time. As we bungle through the next few days, our bodies out of synch with our clocks, we might be asking why we do this to ourselves.

It goes back to an exact moment: noon on Sunday, November 18, 1883. Before that moment everyone lived quite comfortably on local time. Boston was 12 minutes ahead of New York, and New York was four minutes ahead of Philadelphia, but these differences didn't matter to people who travelled on foot or horseback.

With the development of railroads, however, differing local times became a problem. The railroads first tried to cope with their scheduling difficulties by adopting independent times for each railroad. But a city like Pittsburgh that served several eastern and western lines had to maintain five separate clocks to keep passengers "on time."

So the railroads came up with a new plan, which they called Standard Time. There would be four time zones, the time within each zone would be the same, and the zones would be separated by exactly one hour. The whole new system would begin at noon November 18, 1883.

For a while after that transitional moment, people who were accustomed to the sun or local church bells telling them what time it was were disconcerted, but gradually everyone got used to the new time. Then, thirty-five years later, World War I posed a new problem: energy conservation.

Because Standard Time let people sleep beyond sunrise and kept them awake after dark, it required energy to produce artificial light. So on May 31, 1918, clocks were turned forward an hour to another new time called Daylight Saving Time. After the war, laws governing Standard and Daylight Time shifted and changed until 1986, when the pattern we now live by was set by the most recent amendment to the most recent law.

Until new problems arise, we will dutifully "spring forward" an hour the first Sunday in April and "fall back" an hour the last Sunday in October. It's simple enough to change our clocks, but our bodies — like our disconcerted ancestors — are uneasy at first. If you feel uncomfortable in late October, thank biological time, which no one has yet succeeded in standardizing.

Additional Resources? CLICK HERE | Related Article: Daylight Saving Time