It's About Time

It is in people's nature to want to know exactly when something occurred, or when it is going to occur. That's why they invented the calendar.

Today, the entire world uses the Gregorian calendar. Still, the Jewish calendar is used along with about 40 other calendar systems throughout the world.

Established by Pope Gregory in 1582, the Gregorian calendar was influenced by the Jewish calendar. Its main purpose was to replace the older Julian calendar of 45 BCE. Over time, the celebration of Easter had drifted away from its springtime position and its proximity to Passover. In Christian theology, the two celebrations are linked.

The Gregorian is a solar calendar based on the tropical year of the sun and the seasons. Unlike the Jewish calendar, it ignores lunar cycles.

Initially, Protestants refused to follow the new Gregorian calendar, though eventually they fell into line. Eastern Orthodox Christians continue to follow the Julian calendar.

In Israel, there is no legally official calendar. However, all government documents and correspondence use both the Jewish and Gregorian.

The United States has also never adopted an official calendar. Its acceptance of the Gregorian is based on a British Act of Parliament of 1751.

Most calendars number the years in relation to an historical event. Some systems count the years according to the tenure of a reigning monarch. Even Britain, which uses the Gregorian calendar, cited acts of Parliament passed before 1963 by the year of the monarch's reign. A 1925 act would be cited as 15 & 16 Geo.5 (the 15th and 16th year of the reign of King George V).

In the Gregorian calendar, the year number was supposed to designate the number of years since the birth of Jesus. For this reason, the year was always preceded by the Latin 'AD' (meaning: "In the year of our Lord'). Scholars however, think that Jesus was actually born several years before the first calendar year. Jews and many others when using the Gregorian year refer to that period as CE, or "Common Era". The designation BC ("Before Christ") has been replaced with BCE ("Before the Common Era").

The Jewish calendar ensured that religious festivals occurred during the appropriate seasons. Tradition has that it was divinely given. Year number is based on the year of Creation. This would have placed the traditional Jewish date of Creation, according to the Gregorian calendar, on Sunday, September 6, 3761 BCE.

All calendars had to be adjusted every so often so that religious celebrations did not move out of place. The Jewish calendar has an elaborate system to keep lunar months in line with solar seasons.

Like other calendars, it is set up in a cyclical format. It repeats itself every 19 years during which an additional month is added in years three, six, eight, 11, 14, 17 and 19. Each year consists of 12 or 13 months, with each month having 29 or 30 days. When a leap year occurs, the month of Adar with 29 days, increases to 30. The additional month of Adar II is added with 29 days.

Some years are regarded as "deficient" and some as "complete." In a complete year, the number of days in the month of Cheshvan changes from 29 to 30, and in a deficient year Kislev changes from 30 to 29. By contrast, the Gregorian calendar repeats itself every 400 years.

Based on the story of Creation, each week in the Jewish calendar has seven days. The days do not have names, with the exception of the seventh, Shabbat. The entire week leads up to Shabbat. The Gregorian calendar copied this seven-day week.

Both the Gregorian and Jewish years have 12 months, except in a Jewish leap year. The Gregorian year begins January 1st. The Hebrew year begins on the 1st day of the month of Tishrei, the holiday of Rosh Hashanah. The year number changes on that date. The first month is actually Nissan, which occurs in the spring.

The Gregorian day starts at midnight, whereas the Jewish day begins at sundown. Hours are divided into 1080 chalakim (parts). Each celek is 3 1/3 seconds. Throughout the world, all time is set by Greenwich (England) Mean Time, or what is now called Universal Time. In the Jewish calendar, mean time is that of the meridian of Jerusalem.

The Jewish calendar developed a rather complicated system for specific religious reasons (i.e. so that Yom Kippur would not fall the day before or after Shabbat). These adjustments are called dechiyot (postponements).

Ordinarily, the Jewish year consists of 50 weeks plus three, four or five days, depending on the calendar designation of what sort of year it is, as compared to the Gregorian year of 52 weeks. A Jewish leap year, which adds an extra month is 54 weeks plus, five, six or seven days.

The origins of the Jewish calendar are uncertain, though we do know that the basic rules were set down by Hillel II around 400 CE.

When Jews were exiled in Babylon in 600 BCE, they were exposed to the Babylonian calendar. Certain similarities exist between it and the Jewish calendar. The 19-year cycle is common to both. Many of the names of the months are similar. The Babylonian month of Nisannu is the Jewish month of Nisan. Addaru becomes Adar, Tishritu is Tishri, and Abu is Av. This serves as a reminder to many Jews of the exile in Babylon.

The Jewish calendar is lunisolar, combining the cycles of the sun and the moon. The Islamic calendar is purely lunar. It also has a seven-day week and 12 months, with the years beginning from the Era of the Hijra, the migration of Mohammed and his followers from Mecca to Medina in 622 CE. A 30-year cycle is used with 11 leap years in each cycle. As with the Jewish calendar, the day begins at sunset.

Other societies have developed calendars. Calendar reform took place in India in 1957 that established a lunisolar calendar, in which leap years coincide with the Gregorian calendar. Holidays are set according to local and ethnic traditions.

China also uses the Gregorian calendar for administrative purposes, but the traditional Chinese calendar is used for festivals. Of all the calendars, the Chinese is one of the oldest, dating back to the Shang Dynasty of 1400 BCE. Before the 1911 revolution, years were counted from the accession of an emperor.

The Aztecs of Latin America also had a sophisticated calendar system linked to agricultural cycles and various religious ceremonies. It had 18 months, each with 20 days, each week consisting of five days. Its year had 365 days, which included five empty days when all normal activities would cease.

Since many Jews today plan their lives according to the Gregorian calendar, they rely on the calendars they receive from organizations like Chabad to know when to celebrate Passover, Sukkot or the High Holidays, and all the festivals central to Jewish life.