Wednesday, February 29, 2012

Happy Intercalation Day 2012

Today is the day we intercalate, i.e. interpolate or insert, a day in the 365-day solar calendar. This is necessary because the revolution of the earth around the sun takes slightly longer than 365 days, and every few years, we have to "reset" the calendar.
The extra, intercalary day is commonly called a leap day and consequently, the year a leap year. It occurs every fourth year, if and only if the year is evenly divisible by four but not by 100 (unless it is also evenly divisible by 400)!
Other calendars insert leap days, weeks, or months. The Hebrew calendar, for example, is a luni-solar calendar and inserts an intercalary (or embolismic) month 7 out of every 19 years (based on the Metonic Cycle). A leap year in Hebrew is called Shanah Me'uberet (pronounced shah-NAH meh-oo-BEH-reht), literally "a pregnant year." This is necessary to realign the lunar year and the solar year so that the biblical holidays remain in their proper seasons.

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