Give me a second before 2009

This New Year’s Eve is one of those times when a Leap Second is added to the world’s approximately 200 official clocks. So between the end of 2008 and the beginning of 2009, we all will receive one extra second to use and spend however we wish.

An extra second? What is Kevin babbling about this time? Here’s the deal. Leap Seconds operate on the same principle as adding an extra day (February 29) every Leap Year. It is done to keep human clocks and calendars aligned with Earth’s true position. If we didn’t make such corrections, we’d eventually end up celebrating July 4 in Winter and observing midnight after the sun had risen.

The Earth doesn’t rotate at a perfect rate of 24 hours per day. It actually rotates just a little bit more slowly than that, plus its rotation continues to slow over time, so our manmade clocks tend to get slightly ahead of Earth’s natural clock (“natural clock” as defined by Earth’s exact position). As a result, such natural occurrences as sunrise and sunset start to take place a little later than official clocks say they should have. So scientists periodically need to insert an extra second to get human clocks back in synch with the Earth.

We’ve been using Leap Years to adjust the calendar for centuries, but Leap Seconds are a relatively new addition. The first Leap Second was added in 1972, after the point when human timekeeping had become so accurate that we could measure in milliseconds the difference between Earth’s position and our clocks.

Want to learn more about Leap Seconds?

• This article on Space.com provides additional detail about the Leap Second to be added between 2008 and 2009.
• The Wikipedia article on Leap Seconds explains the technical details, as well as provides a calendar of all of the Leap Seconds that have been added since the process began in 1972.
• For an example of what can happen when Leap Years and Leap Seconds are not observed, check out this article about how George Washington’s birthday shifted from February 11 to February 22 while he was growing up, due to the inaccuracies of the calendar of his time.

But no matter what, make sure to enjoy your extra bonus second of time at the end of this year! After 2008, I think we’ve all earned it.