Why is jewish calendar different

Years are either 12 or 13 months, corresponding to the The lunar month on the Jewish calendar begins when the first sliver of moon becomes visible after the dark of the moon.

In ancient times, the new months used to be determined by observation. When people observed the new moon, they would notify the Sanhedrin. When the Sanhedrin heard testimony from two independent, reliable eyewitnesses that the new moon occurred on a certain date, they would declare the rosh chodesh first of the month and send out messengers to tell people when the month began. The problem with strictly lunar calendars is that there are approximately The months drift around the seasons on such a calendar: on a month lunar calendar, the month of Nissan, which is supposed to occur in the Spring, would occur 11 days earlier in the season each year, eventually occurring in the Winter, the Fall, the Summer, and then the Spring again.

On a month lunar calendar, the same thing would happen in the other direction, and faster. To compensate for this drift, the Jewish calendar uses a month lunar calendar with an extra month occasionally added.

The month of Nissan occurs 11 days earlier each year for two or three years, and then jumps forward 30 days, balancing out the drift. In ancient times, this month was added by observation: the Sanhedrin observed the conditions of the weather, the crops and the livestock, and if these were not sufficiently advanced to be considered "spring," then the Sanhedrin inserted an additional month into the calendar to make sure that Pesach Passover would occur in the spring it is, after all, referred to in the Torah as Chag he-Aviv, the Festival of Spring!

Note that the traditional Chinese calendar follows the same sort of procedure, occasionally adding months to keep in sync, which is why "Chinese New Year" is always around late January or early February and Yom Kippur usually coincides with a Chinese fall festival I'm not sure which one, but Chinatown is always very busy for the holiday the night when I break my fast!

The Islamic Hijri calendar, on the other hand, is strictly a lunar, month calendar so the fasting month of Ramadan could fall in short, cool days of January as it will in the late s or in the long, hot days of August as it did in the early s.

An Islamic friend of mine once told me she preferred when it landed in January! In English, we commonly call it a leap year. Note that Adar II is the "real" Adar, the one in which Purim is celebrated, the one in which yahrzeits for Adar are observed, the one in which a year-old born in Adar becomes a Bar Mitzvah.

Adar I is the "extra" Adar. What does a leap year look like in the Jewish calendar? When do holidays begin and end? Why do some people celebrate a Jewish holiday for one day and others celebrate the same holiday for two days? Is there a holiday for the new moon? Are the Jewish holidays interconnected? Is there an overarching structure to the Jewish calendar? Two holidays serve as signposts for these respective seasons — Passover , the spring festival of freedom that begins on the full moon on Nisan March or April in the Gregorian calendar , and Sukkot , the fall harvest festival that begins exactly six months later on the full moon of Tishrei September or October in the Gregorian calendar.

Each recalls — or actually, recreates — a different historical journey: on Passover, the journey from slavery in Egypt to freedom on the far side of the Red Sea; and on Sukkot, the year journey through the desert to the Land of Israel. The progression begins with Hanukkah , which comes in the darkest days of the year and recalls the miracle of oil in the Jerusalem Temple that burned for eight days.

Unlike our secular day, in which the daylight hours are framed by night, the Jewish day begins with night and ends with day. This is the reason why all Jewish holidays begin in the evening before the first day of the observance.

In fact, according to a Jewish reckoning of time, the evening before the day is indeed the beginning of the new calendar day. The first story of creation in Genesis also establishes the next higher unit of measuring time, namely the seven-day week. This tale serves to place the week firmly within the divine plan, in which a six-day workweek is followed by the sacred Sabbath , a divinely ordained day of rest. Since most units of measurement ultimately go back to the Babylonians , who were the first great astronomers and natural observers of the ancient world, we know that the week is meant to be coordinated with the four phases of the moon.

Therefore, roughly speaking, four weeks make a month. And roughly 12 months make a year. Since, however, the month lunar year and the day solar calendar do not overlap exactly, the Gregorian calendar that has become the standard world calendar has months of unequal length that no longer correlate with the phases of the moon and has to insert an extra day every four years the leap year in order to have the calendar reflect the solar year.

This becomes somewhat more complicated in the case of the Jewish calendar , for it is still coordinated with the phases of the moon. An extra month is intercalated every 3 years, based on a cycle of 19 years.

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