Seven Times in 19 Years
This year (5784) is a leap year in the Jewish calendar, which means we’ll be following the month of ADAR with the sequel ADAR 2 right after. This also means that we will have to wait a little longer to celebrate the Jewish anti-Halloween Purim because all the fun Adar holidays are deferred until ADAR 2: Electric Boogaloo.
So, with this said, is Purim “later” or “earlier” than usual? And when we say “usual,” usual in comparison to what?
Well, the short answer is “the Christian Calendar.” Folks call it the “Gregorian Calendar” for reasons I will explain shortly. The Gregorian Calendar marks the birth of Jesus as its “Year Zero,” except most historians will tell you that Jesus was probably born in either 3 or 4 BCE. The Gregorian calendar is also a solar calendar.
As you know, the Earth is round and it revolves counterclockwise around the Sun in an elliptical orbit. The Earth rotates counterclockwise around an axis that is tilted 23.5 degrees. In the northern hemisphere, the day is longest at the June/Summer solstice and shortest at the December/Winter solstice. At the two equinoxes – Vernal (Spring) and Autumnal (Fall) – day and night are equally long.
Before Pope Gregory XIII (of “Gregorian calendar” fame), Europe used the Julian Calendar, named after Julius Caesar who instituted it in 46 BCE. For 1,500 plus years, it was believed that the solar year was 365.25 days long. Thus, the Julian calendar had 365 days with an extra day added every fourth year to round things out. Mathematicians soon discovered that the Julian calendar gained .0078 days every year on the true solar year, adding three days every four centuries.
A correction was made in 325 CE, but by the time of Pope Gregory XIII, the calendar was ten days off. So Pope Gregory XIII decided to erase October 5-14th, 1582 from the calendar. And to correct for the fact that three days were gained every four centuries, Pope Gregory XIII decreed that the “leap years” of the former calendars were to be dropped on dates ending with two zeros, unless the first two digits were able to be evenly divided by four.
This change was not perfect, but it only adds one day every ten thousand years – so the Gregorian Calendar is pretty good!
When it comes to holydays, Jews do not use the Gregorian calendar. (When it comes to coffee dates, we do.) Rosh Chodesh Adar marks the launch of the new month with the appearance of the New Moon. The word “moon” and “month” are cognates. But before you put us solidly in the Lunar Calendar camp with Muslims worldwide, recall that ancient Jews were mostly farmers who were deeply rooted in the agricultural cycle… which is based on the position of the earth vis-a-vis the sun, which also determines the seasons. In other words, Jews use BOTH.
The Jewish calendar is a Metonic calendar, named after the Greek astronomer Meton of Athens, who observed that that a period of 19 solar years is almost exactly equal to 235 synodic (or lunar) months. Rounded to full days, they both total 6,940 days. BUT WAIT! 19 years of 12 synodic months equals 228 months – NOT 235 months. We will fall short! So Meton came up with a clever solution: Add a “leap month” seven times over 19 years. In this way, our seasonal agricultural/pilgrimage holidays fall in the right season every time. Sukkot will always fall in the fall. Passover will spring in the spring and Shavuot will fall seven weeks later in the summer. And Purim will always fall in Adar… but because we’re adjusting this year with a leap month, Purim isn’t as much “late,” but like many flights on Air Canada, only slightly delayed.