Oh, Those Pesky Calendars!

There are lunar calendars and calendars based on the solar year. Sometimes, when we use both to determine specific dates, wackiness ensues.

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Today is March 31 by the modern calendar, the Gregorian calendar adopted in October 1582 across much of the Christian-influenced world. Pope Gregory XIII published a church document, Inter Gravissimas, to update the older Julian calendar with a change to leap years to better match the calendar year with the solar year. The older Julian calendar had a few too many leap years, and over the centuries scholars noted that the March equinox was occurring well before the nominal March 21 date, so a bit of tweaking was called for.

The Gregorian calendar is the one we use for most common scheduling purposes. On this calendar, March 31 is Freedom Day in Malta, Caesar Chavez Day in the United States, Día Nacional del Girasol in Argentina, and the . This date is also Anesthesia Tech Day and Dance Marathon Day, as well as National Tater Day, celebrated since 1843.

Now, there are other calendar systems used in the world, including lunar calendars, counting time from the phases of the moon. Since the lunar month, the time lapsed from one full moon to the next for example, don’t divide…