September 2, 2011 - Last Day of the Julian Calendar

– 1752

This old calendar from
Thessaloniki shows various
different dates used by 
different people. The upper
left date is from an Islamic 
calendar, the upper right is
the date according to a Jewish
calendar. The lower dates are from
Julian (left) and Gregorian (right)
In Great Britain and all the British colonies, including the American colonies, Saturday, September 2, 1752, was the last day of an outdated calendar. The next day was Sunday, September 14, 1752.

The switchover from the Julian to the Gregorian calendar was made because the Julian calendar was getting more and more out of sync with the seasons. We want the winter months to correspond to the cold season of the year, for example. The Julian calendar was quite a bit like the Gregorian calendar, which is what we use today. The Julian calendar even added an extra day to February every four years, like we do, to make sure that the calendar and the seasons stayed in sync. So... what happened? How did the calendar and the seasons get out of sync?

Well, the actual year is not 365-and-one-quarter days long, as the ancients believed. Instead, the year is 11 minutes shorter than that. Just 11 minutes difference—but that difference added up over the years and over the centuries. All those 11 minutes added up to so much difference that, by the time Britain finally adopted the updated calendar system in 1752, people had to skip 11 entire days—which means skipping 15,840 minutes!

(The Gregorian calendar keeps better sync with the seasons by skipping three leap year days every 400 years. It's complicated!)

Calendar reform was controversial in
Britain during the 1754 election. If we could see
this William Hogarth painting up-close, we would
see a sign that reads, "Give Us Our 11 Days!"

Just picture living in 1752: Maybe your birthday is September 6. Well, that year, there was no September 6! Do you celebrate on the 17th? Actually, you have a problem for the rest of your life—do you stick with your birthday being September 6 (according to the old calendar you no longer use), or do you refigure your birthday according to the new calendar?

Note that different countries switched from the Julian to Gregorian calendars at different times—from Italy (Holy Roman Empire) and Spain in 1582 to Russia in 1918. The fact that different countries were using different systems really made a mess of things!

For more on the long-drawn-out switchover, check out this earlier post.

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