When is your birthday this year? You could be celebrating your birthday a day too early, or perhaps a day too late. Our custom is to celebrate (or lament depending on your age) our birthdate every year, which is essentially celebrating the earth making yet another revolution around the sun (the “solar" calendar).
The problem is that the earth doesn’t make a full revolution in 365 days….our traditional calendar falls short by 6 hours, 11 minutes and 26 seconds. That means that if you were born at 9:00 and night, your birthday on the solar calendar (when the earth returns to the same exact spot) is technically 6 hours later, or 3:00 am the next day. You celebrated your birthday too soon!
However, if you happened to be born on a leap year, then when your next next calendar birth date comes around, you are actually one year and one day old (the earth has already passed by the original spot of your birthday). Hence, your birthday on the solar calendar was yesterday!
Now you say, hold on a minute. Doesn’t this average out year after year, adding the leap days every four years? The answer is: yes, mostly it does. Your calendar birthday keeps sliding later and later compared to the solar calendar until the leap day jumps ahead to catch up. Unless you were born on a leap year, then your birthday is technically a day too early and it keeps sliding back closer and closer to the actual solar birth date until leap day leaps ahead again.
The calendar we traditionally use (at least us here in the western civilization) is called the Gregorian calendar. It was Julius Caesar who created the Julian calendar, which attempted to synchronize the calendar with the solar calendar by adjusting for those missing 6 hours and adding a leap day every four years.
Unfortunately, the Julian calendar did not compensate for the missing 11 minutes per year. By the 1500’s, those 11 minutes accumulated to the point where the Julian calendar and the solar calendar were off by as much as 10 days. This problem had religious overtones since the relationship between the date for Easter and the spring equinox were significantly out of sync. In 1582, Pope Gregory XIII (i.e. the "Gregorian" calendar) unveiled a new calendar which made an adjustment for those missing 11 minutes by skipping a leap year in three out of four century years.
ANSWER TO TRIVIA QUESTION:
In 1752, England was still using the Julian calendar whereas the rest of Europe had been using the Gregorian calendar. By then, England’s calendar was off by nearly 11 days. Hence, Parliament voted to follow Wednesday, September 2 with Thursday, September 14. Nothing ever happened in England between September 3 and 13, 1752…those dates didn’t exist.
Unfortunately, we are not done yet….one more adjustment is going to need to be made. To be exact...the solar calendar and the Gregorian calendar are still off by 26 seconds per year. We are going to have to add another leap day by the year 4949.
Somebody mark your calendar will ya?
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