Some moon talk as Adar 2 nears

As February turns to March on the Gregorian calendar, the Hebrew month of Adar Aleph becomes Adar Bet on March 3. The second Adar, comes seven times every 19 years on the Hebrew calendar.

Traditional lore attributes the standardization of the Hebrew calendar — in which the months follow the course of moon, but are aligned with the seasons — to Hillel II, leader of the Sanhedrin in the 4th century. Experts believe the evolution of the calendar was much more gradual.

“The Bible contains some basic references to solar and lunar elements, but it does not lay out clear rules. Over time, these emerged, and by the rabbinic period the calendar looked very similar to the one we use today, although there were sectarian groups who did not accept it and had their own traditions of calendar rules,” Elisheva Carlebach, professor of Jewish history, culture and society at Columbia University, told JNS.

Sasha Stern, head of the Department of Hebrew and Jewish Studies at University College London, told JNS that “a lot of people use the word ‘lunisolar’ to indicate that the calendar is regulated by the moon (which defines the beginning of the month) as well as by the sun (which demands the addition of 13th lunar month every two or three years).”

But a core aspect of the original establishment of a Hebrew calendar was the need to determine the timing of religious holidays.

“In the Jewish calendar, the addition of a 13th month is required for keeping up with the seasons (e.g. spring for Passover), not with the sun,” he said. In meteorology, the schedule of the seasons does not quite correspond with the movement of the sun.

Stern believes the term “lunisolar” is a misnomer. The lunar year is 12 lunar months of an average of 29 and a half days each, with a total of approximately 354 days in a year, he explained. “This falls short of the seasons by about 11 days,” and thus “an extra month needs to be added every two or three years in order to make up for this and keep up with the seasons,” he said.

The ancient Israelite calendar was therefore most likely lunar, with 12 months, each beginning with a new moon. Stern said all lunar calendars in the world “have always added a 13th (leap) month,” with the exception of the Islamic calendar.

According to Rabbi Menachem Posner, an Ask the Rabbi respondent on Chabad.org, the 13th month was once added by the Great Court in Jerusalem on a case-by-case basis.

“In the modern Jewish calendar, this has been placed on autopilot following a predetermined 19-year cycle,” he said. “This means that the extra Adar is added every two or three years.”

After the destruction of the first Temple, Jews adopted the Babylonian calendar, from which the names of modern Hebrew months originate.

“The Babylonian calendar was very influential, as the Jews adopted it almost whole piece in the 6th century BCE,” Stern said. “In the Babylonian calendar, the addition of a 13th month was required for keeping up with certain stars.”

Experts believe that after the rise of Christianity, the Christian and Hebrew calendars influenced each other. Easter originally took place around Passover, but eventually came to be calculated separately. This also influenced the evolution of the Hebrew calendar from one based on moon sightings to one based on calculation.

Additionally, for centuries since the Middle Ages, “calculating the date of Easter and trying to separate that calculation from direct dependence on the Passover of the Jewish calendar occupied the energies of great Christian theologians,” Columbia’s Carlebach said.

A fixed Hebrew calendar was finalized in the 10th century. Some diversity persisted well into the medieval period, but the fixed calendar became largely universal over time.

Carlebach writes that following the 15th century in Europe, Jews began to treat calendars not only as conceptual measurements of time, but as material things. Manuscripts of the Hebrew calendar began to circulate. The printing revolution allowed for the reprinting of the calendar, not only by Jews but also by Christians.

In addition to the calendars themselves, other materials circulated such as “Ibburim,” which explained how to compute the equinox and solstice. The first printed Ibbur was edited by a Catholic calendar expert, Sebastian Münster. His partially translated edition included a standard Catholic calendar with both Saints Days and the names of the Jewish months in Hebrew in the margins.

The Jews took note of Christian holy days in their calendars, both to avoid potential persecution, which tended to occur more often on holy days, but also for trading purposes. Christian market fairs often took place on holy days.

Besides the well-known incidence of Purim Katan, Hebrew leap years can present interesting scenarios. For example, Posner asked, if a boy was born in a regular year but his bar mitzvah falls on a leap month, “When does he reach the age of majority?”

“In practice we do not count him for a minyan or call him up for an aliyah to the Torah until after his Adar II birthday. However, because of the possibility that the boy reached adulthood in Adar I, he should begin laying tefillin in Adar I,” said Posner.

On yahrtzeits, “some people mark them only on Adar I and others mark them just on Adar II,” Posner noted.

“Since this is a contested issue, many observe yahrtzeit twice [during a leap year],” he said.

While the age-old intricacies of the Hebrew calendar aren’t novel, the calendar is gaining newfound relevance in Israel today through a Knesset bill that was approved in a preliminary reading Feb. 26. The bill stipulates that official identification issued to Jewish citizens should use Hebrew calendar dates, instead of the Gregorian dates commonly used worldwide.

Member of Knesset Elazar Stern (Hatnua) said regarding the bill that the Hebrew calendar “is an integral part of the history of the Jewish people,” Israel National News reported.

“This bill, which would increase the use of the Hebrew date, is another step in strengthening Jewish democratic character of the state of Israel,” Stern said.