Have you ever wondered why we have time zones? You can thank the American railroads.
Prior to 1883, every city in the world kept its own unique local time. Everyone used the same format of hours, minutes and seconds. But each city would base its “noon” on when the sun was most directly overhead. As a result, your local town might mark noon several minutes earlier or later than the town a few miles down the road.
This was not a problem when people spent most of their lives in one place. But with the advent of railroads, people could easily travel far and wide. And people expected the railroads to run on time. This was not easy when there was no universal definition of “on time.”
The U.S. alone had more than 300 different time zones. The railroads tried to improve things by establishing 100 “railroad times zones.” Needless to say, this did not help much.
Finally, on November 18, 1883, the U.S. adopted four standard time zones. If your city was at the western end of a time zone, you would mark noon a little earlier than actual solar noon. And if your city was at the eastern end, you would mark it a little later.
A year later, Britain drove international support for global time zones. But there was disagreement about whether to base the standard on Paris or Greenwich Mean Time. This argument was not fully resolved until 1978! (For years, the French defined “legal time” as Paris Mean Time minus nine minutes and 21 seconds.)
Fun fact: China, which geographically covers almost 60 full degrees of longitude, standardizes the entire country on a single time zone.
In 1916, Germany and Austria-Hungary introduced Daylight saving time, where evening daylight would last an hour longer during summer months, to save on energy costs during the Great War. The U.S. adopted DST in 1918, repealed it in 1919 (after the war), re-implemented it from 1942 to 1945 (during World War II), re-implemented it again in 1974 (during the energy crisis), and made it permanent in 1986.
Daylight saving time remains controversial. Messing around with your 24-hour circadian cycle can drastically affect your mood. In fact, researchers recently found that DST’s shift back to standard time in autumn is closely linked to an 11 percent spike in depression.
In an earlier study, researchers used an Agilent Bioanalyzer system to study the link between major depressive/bipolar disorders and circadian rhythms. They found that dysregulation of the CRY2 gene (a circadian gene that regulates the human body’s evening oscillator) is significantly associated with winter depression.
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