Although one day and night are supposed to last for 86,400 seconds, the total is closer to 86,400.002.
Because our clocks are exact but the earth is not, little by little the time creeps away from where we think it should be. Doing nothing, eventually we would be having lunch in the moonlight.
To maintain a clock and sun sync, since 1972 we’ve added 26 leap seconds. And now, with the addition of another leap second on December 31, 2016 at 23.59.59, the clocks will go to 23:59:60 rather than 00.00.00. My leap second on the U.S. East Coast will be at 18:59:59.
Even with leap seconds, many clocks aren’t sun-coordinated. The extreme case is China and its single time zone. Awakening 2,000 miles west of Beijing at 10 am, you could see the stars.
Our Bottom Line: Standardization
Whether looking at weights and measures or leap seconds and time zones, we are really talking about standardization. A shared system of time and weights and measurements enables commerce to function efficiently,
In the U.S., Thomas Jefferson was wise enough to encourage standardization in his 1790 report to Congress, “Plan For Establishing Uniformity in the Coinage, Weights, and Measures of the United States.” Continuing the principle that the federal government is responsible for uniformity, the National Bureau of Standards, now known as the National Institute of Standards and Technology (NIST) was established in 1901.
As for the time, it took the railroad to establish some uniformity. Traveling from town to town during the 1830s meant constantly changing your watch (if you had one). By the 1850s, though, local time started becoming railroad time. The invention of the telegraph enabled the same time to be communicated from place to place. As a result, railroads gave conductors, engine drivers, switch tenders and bridge tenders “a good watch.” The conductor was responsible for coordinating the watches before each departure and making sure that stations along his route had the same time.
Once the stations had the time, so too would the town. After all, if you were picking someone up at the station or your supplies were arriving by train, you had to know the time. Local time? No. The railroad’s time.
Now, almost 200 years later, even leap seconds are standardized.
My sources and more: Thanks to Vox for reminding me of the leap second, to Wired for more detail, to the IERS for the data and the NY Times for my China facts. But if you have more time, Keeping Watch: A History of Time is the book to read. Please note than most of Our Bottom Line was excerpted from a previous econlife post. Also, this post was corrected. 86,400.02 should have been 86,400.002.