How Daylight Saving Time Works

adjusting clock adjusting clock
Howard Brown adjusts the time on a clock he just repaired as he hangs it on the wall at Brown's Old Time Clock Shop in Plantation, Florida. He'll have a lot of clocks to adjust in anticipation of daylight saving time. Joe Raedle/Getty Images

According to astronomers, the big bang created both time and space about 14 billion years ago. Ever since, seconds and minutes have spooled outward, like an infinitely large ball of twine unraveling as it rolls on a ceaseless journey. Humans have long tried to affect this unraveling process, to make it happen more slowly or quickly. Einstein even predicted it was possible -- if we could travel at the speed of light. Unfortunately, most of us will never ride on the back of a light beam. Instead, we must be contented with the nonrelativistic speeds we can attain in jets and Jettas, which means we must also be satisfied with time that is universal and constant.

Still, we're not complete slaves to time. Humans have devised ways to manipulate it to their advantage. daylight saving time (DST), the period of year when clocks are moved one hour ahead to create more sunlit hours in the evening, stands as one of the best examples of how this can be done. Benjamin Franklin first conceived of DST in 1784, while serving as U.S. ambassador to France. According to the story, he woke one day at 6 a.m. and noticed how many of his fellow Parisians were still in bed, with shutters drawn to keep out the light. As a result, people were sleeping during sunlit hours and burning candles longer into the evening. What if, Franklin wondered, people adjusted their schedules to make better use of the longer summer days? Wouldn't that save large amounts of tallow and wax?

Of course, Franklin didn't know how to implement such an idea. One of his first thoughts was not to shift the day forward by an hour, but to use cannons to wake everyone at the desired time. Although Franklin proposed his ideas in an article, you get the feeling he was having fun with his readers, warming his mental muscles for larger problems and grander inventions. Whatever the case, Franklin never actively pursued the matter again, and more than a century would pass before daylight saving time would get serious attention as a viable timekeeping option.

Today, many people all around the world take DST for granted because it's such an integral part of the annual routine. The fact that it's an old idea takes people by surprise. It's just one of the many surprises this article will reveal. Let's begin with how daylight saving time works and what, exactly, happens when we "spring forward" and "fall back."