Jewish Leap Year

February is here!  A new month and we begin our rhyme:

Thirty days hath September
April, June, and November,
All the rest have thirty-one,
Excepting February, which stands alone,
And that has twenty-eight days clear
And twenty-nine in each leap year.

February is the shortest month at only 28 days, but as we know every 4 years, we get a leap year.  This extra day helps to compensate for the fact that a period of 365 days is shorter than a tropical year by almost 6 hours.  The tropical year is the time that the sun takes to circle and return to the same position in the cycle of seasons.   For example, the time from vernal equinox to vernal equinox, or from summer solstice to summer solstice.

But what you might not know is that the Jewish calendar also has leap years!  Unlike the Gregorian calendar, which is based on a solar cycle, the Jewish calendar is based on the lunar cycle.  The beginning of the New Month (Rosh Chodesh) begins when the crescent of the moon can be seen in the sky.  In ancient times, this new month was determined by observation.  When people observed the new moon, they would notify the Sanhedrin, the assembly of Rabbis that made up the tribunal of each city.  When they heard testimony from 2 independent reliable witnesses that the new moon had occurred on a certain date, then they would declare Rosh Chodesh and send out messengers to tell people when the month began. 

The problem with a solely lunar calendar is that there are 12.4 lunar months per solar year.  This causes a problem because the holidays can then drift out of their designated season due to the fact that a 12-month lunar calendar is about 11 days shorter than a solar year and a 13-month lunar calendar is about 19 days longer.  To compensate for this drift, the Jewish calendar uses a 12-month calendar with an extra month occasionally added.  For example, the month of Nissan occurs 11 days earlier each year for 2 to 3 years and then jumps forward 30 days to even everything out.  In ancient times, this month was added by observation of the weather, crops, and livestock to see if they were sufficiently “spring like.”  If not, they added a month to make sure Passover, also know as Chag he-Aviv, the Festival of Spring, would actually occur in spring.  Sort of like an original Groundhog Day!

By the 4th century, Hillel II established the fixed calendar we have now that is still in use.  The extra month was decided to be Adar because it is considered happy and lucky.  In a leap year, an extra month is added called Adar Aleph, Adar Rishon or Adar I.  This is followed by Adar Bet, Adar Sheni or Adar II.  The first Adar is considered the “extra” month.  Adar IIis considered the “real” Adar and is the one in which we celebrate Purim, mark yahrzeits for Adar and in which a 13-year-old born in Adar becomes a Bar or Bat Mitzvah.   

The Jewish leap year, or Shanah Me’uberet (literally pregnant year in Hebrew) occurs 7 times every 19 years, with years 3, 6, 8, 11, 14, 17 and 19 of the cycle being leap years.  This means it occurs every 2-3 years.  It may sound complicated, but by using this system the Jewish calendar only deviates from the solar year by 1 day in 216 years. 

This year, we are in a leap year.  Adar Ibegan on February 5th at sunset.  Purim Katan, the festive day in Adar I, was on February 19th.  Adar IIbegins on March 7th at sunset.  We celebrate Purim on March 20th.  So, if you have ever wondered why Rosh Hashanah (or insert any Jewish holiday here) is so early or so late this year, I hope this explains why!