The Secret Jewish History of Leap Year

This year is Leap Year in both the secular Gregorian calendar — the one most of the world goes by — and in the Hebrew calendar. Because both calendars count time in measures that round off days, months, and years, and base these measures on different astronomical phenomenon, both are “corrected” periodically so that fixed dates and seasons don’t drift too far off course.

Not all calendar systems care about this sort of thing. The Islamic calendar, for example, measures time solely by the moon cycles, and as such, Muslim holidays and festivals like Ramadan and Eid occur at varying times of the year – or rather, at various times during the natural seasons. They always occur on the same Islamic dates; it’s just that the dates aren’t fixed to the solar, or seasonal, calendar in any way.

The Hebrew and Gregorian calendars, for various historical, astronomical, social, and religious reasons, are set up so that holidays like Passover and Easter always occur in the spring, in keeping with their nature and history. They achieve this by periodically intercalating days or months to keep things “on schedule.”

This is most plainly and simply illustrated, of course, with the Gregorian calendar’s intercalation, almost every four years, of an extra day in February, giving the shortest month of the year an extra “Leap Day” on February 29, as is the case this year. There are a few exceptions to this practice, however. The Gregorian calendar, a solar-based calendar, removes three leap days every 400 years, which is the length of its leap cycle. In the three century years (multiples of 100) that cannot be exactly divided by 400, there is no February 29. Thus, the year 2000 was a leap year, and 2400 will be a leap year, but 1800 and 1900 where not, and, for those of you planning ahead, the century years of 2100, 2200, 2300, and 2500 will be “regular” years in which February will only have 28 days and the year will only be 365 days.

The Hebrew calendar is a bit more complex, being a “lunisolar” calendar that simultaneously is dependent upon cycles of the moon to measure months and cycles of the sun to measure the lengths of the day and the year. This might not intrinsically be such a big deal, but when your religious obligations include blessing and sanctifying each new month, it’s pretty important to get the timing of the months correct.

Back in Babylonian times, the observance of the new month was based upon just that — the appearance of what we now call the “new moon,” meaning no moon. To insure that Jews throughout the greater Middle East were all on the same calendar page, fire signals were passed along from station to station in the mountain country between Jerusalem and Babylonia. This worked well until the second century of the modern era, when mischievous Samaritans, in order to confuse the Jews, purposely lit fire signals at the wrong times, thus sabotaging this method of reckoning the new moon across the Jewish world.

Rabbi Judah, the nominal head of the Sanhedrin at the time, subsequently abolished the fire-signals and employed messengers instead to ride like Paul Revere from town to town declaring the onset of the new moon. But without high-speed railways, this method was short-lived and doomed to fail, and thus sages finally resorted to astronomical calculations to once and for all fix the months and the festivals and the years. Credit for this is typically awarded to the Patriarch Hillel II in the fourth century.

But as previously noted, the problem with strictly lunar calendars is that there are approximately 12.4 lunar months in every solar year, so 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 than a solar year. Strictly followed, the months would drift around the seasons, and the month of Nisan, which is supposed to occur in the spring, would occur 11 days earlier in the season each year, such that over time Pesach would be celebrated in all four seasons.

So in the same way that the Gregorian calendar adds an extra day to February every four years, the Hebrew calendar intercalates a complete month over the course of a 19-year cycle, called the “Metonic” cycle, so that the lunar calendar realigns with the solar years. Adar I, or Adar Rishon, is added in the 3rd, 6th, 8th, 11th, 14th, 17th and 19th years of the cycle, including in this Hebrew year of 5776, when Adar I began on February 10.

Adar II, or the “real” Adar, in which Purim (this year arriving “late” on March 24) always takes place, follows (beginning this year on March 11), and brings the year to a close before the new year of Nisan. (Why the new year begins with Nisan as opposed to on Tishrei’s Rosh Hashanah – which typically appears in early autumn – is another story for another day.) Some find significance in the fact that in Hebrew leap years, we duplicate the month of Adar, which is also known as “the lucky month.” So we get a double dose of luck every leap year.

And now for some Hebrew leap year trivia as well as the secret Jewish history of February 29:

  1. A year with 13 months is referred to in Hebrew as shanah me’uberet, or, literally, a pregnant year.

  2. According to Maimonides, the arithmetic of the Hebrew calendar does not require any major mathematical skills. “… the method of the fixed calendar is one which an average school child can master in 3 or 4 days,” he wrote (Hilkhot Qiddush HaHodesh 11:4). With all due respect and humility before the great Rambam, I disagree. Or, perhaps, I am a mathematical imbecile.

  3. Some believe that human efforts to reconcile the lunar year and the solar year represent a partnership with God, and that in the Messianic Era, we will revert to a completely lunar calendar.

  4. Considering it only pops up once every four years, February 29 has proven to be a somewhat auspicious date in Jewish history. It was on this date in 1868 that British-Jewish Prime Minister Benjamin Disraeli formed his first cabinet. It was also on this date in 1988 that a Nazi document was discovered implicating participation of Austrian president and former U.N. Secretary General Kurt Waldheim in World War II deportations. Former Israeli prime minister, longtime politician, and military leader Yigal Allon died on February 29, 1980.

  5. Jewish-American singer-actress Dinah Shore was born on February 29 in 1916, and Pulitzer Prize-winning poet laureate Howard Nemerov (older brother to photographer Diane Arbus) in 1920. Someone born on this date is called a “leapling.”

  6. Al Rosen, one of the greatest Jewish baseball players of all time, was born on February 29, 1924. The four time all-star and legendary home-run hitter played a decade for the Cleveland Indians in the 1940s and ‘50s and inherited his hero Hank Greenberg’s nickname, “The Hebrew Hammer.” A former boxer, Rosen was known for challenging opposing ballplayers to fight whenever they taunted him with anti-Semitic slurs. Rosen refused to play ball on the High Holy Days, undoubtedly influencing Sandy Koufax after him.

  7. This year, on February 29, 95-year-old Hubert Zafke, a former medic at Auschwitz, will go on trial in Germany on at least 3,681 counts of accessory to murder.

Seth Rogovoy is a Forward contributing editor.

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