Hey this is probably a really dumb question but does the Jewish calendar have a leap year?
Yes it sure does! Its called a shana meuberet, a pregnant year.
The Jewish calendar is Lunar-Solar. Its an approximate solar year with months that follow the lunar cycle. However, there are slightly less than 12 lunar cycles in a full solar year, so, a purely lunar calendar would gradually “slide” off of solar/seasonal time without a leap year, and thats not possible for the Jewish calendar, because we need our holidays to be tied to the seasons they represent, because they’re agricultural.
But, you can’t insert an extra day or week, because that would knock the months out of phase with the moon, which is also unacceptable for religious reasons - almost all Jewish holidays occur on (or very near) a full or new moon.
In the ancient world, sightings of the new moon in Jerusalem were used as the beginning of each month, announced via shofar and a system of messengers. (The reason some holidays have an “extra” day outside of Israel in many minhagim, like Shavuot, Pessach day 2, Rosh Hashana, etc, is so that people who lived farther than a days ride from Jerusalem would still be able to celebrate the holiday.
Also in the ancient world, they would adjust the calender based on the growth stage of barley around the time of Pesach. If the barley wasn’t ripe by the time the moon changed, they would wait for another month.
And that’s how the Jewish leap year works! We add a whole extra month. Specifically, the extra month before Pesach! Kind of. Because Purim is supposed to always fall four weeks before Pesach as a beacon of anxiety, the extra month is actually Adar א, Adar 1. And the normal month of Adar with the holidays and fasts which occurs in all other years becomes Adar ב, or Adar 2, the 13th month.
Now, just like the Gregorian calendar, we now rely on mathematical formulas derived from celestial observation, instead of directly using celestial observations as a clock. It works better. (But the Hebrew calender still has a tinnnnnyyyy gap, and is very very slowly creeping forwards, which is why Thanksgivikah will never happen EVER again, actually.)
The pattern for leap years by number is a 19 year cycle, with 7 leap years, with the 3rd, 6th, 8th, 11th, 14th, 17th, and 19th years being leap years.
12 12 (13) 12 12 (13) 12 (13) 12 12 (13) 12 12 (13) 12 12 (13) 12 (13)
My favorite fun fact of all time is that you can remember the pattern of Jewish leap years with the intervals of the major scale. (A whole tone is analogous to three years, and a half tone is analogous to two years.)
W W H W W W H
Its harder to write down because there are multiple ways you could visualize it, but, once you get it you won’t forget it.
