Special Leap Day Astrominute

Sorry, I haven’t posted on of these in while. Hope you’ve been hearing them on WZBT. This one’s all about Leap Day – there may be more to it than you think.

MP3 here: http://public.gettysburg.edu/~iclarke/hatter/podcasts/astrominute022516.mp3

Text below:

Here is a special Gettysburg Astrominute for Leap Day. There it sits, at the bottom of your calendar: February 29. The story of our leap day goes back to the days of Julius Caesar, who had a problem to solve. The poor Romans, with their 355-day calendar, had to periodically add days (to February, usually) to keep their agricultural festivals occurring in the right season. In 46 BC the Julian reforms regularized the practice to one day every four years. If you think that’s the system we used today, you’d be wrong. A seasonal year is actually about 11 minutes less than 365.25 days, and by the 1500s, this error had added up to ten days. Reforms under Pope Gregory XIII added in the missing ten days and introduced a couple of tweaks that result in 97 leap days every 400 years – enough that a calendar year and a seasonal year are now practically the same. The tweaks were to skip leap years in century years, except those divisible by 400. Thus, 1900 was not a leap year, but 2000

was. The new system was adopted right away in Catholic countries, but not so fast elsewhere. Great Britain and its colonies held out until 1752. Folks living then, our founding fathers included, got to decide which birth date to use, old style or new. Russia did not adopt the reforms until after the 1917 revolution, meaning that, as far as most of the world was concerned, the October revolution happened in November. The astrominute is produced by Gettysburg College’s Hatter Planetarium and WZBT.