As the sun sets tonight around the globe, Jews worldwide will begin the celebration of their new year, Rosh Hashana, which, according to the Jewish calendar, ushers in the 5,761st year since the creation of the world.
Rosh Hashana serves as a reminder that while much of the world marks time by the Gregorian calendar, established in the 16th century by the Roman Catholic Church, other cultures and religions mark their days, months, years and eras differently. And it also shows that any calendar is essentially arbitrary, as those who devise it must select some fixed date as a starting point.
So when does time begin?
FOR THE RECORD - An article in yesterday's editions of The Sun incorrectly described the 16th-century calendar reform led by Pope Gregory XIII. A papal bull ordered that days be omitted from the Western calendar, so that Oct. 4, 1582, was followed by Oct. 15, 1582.
The Sun regrets the error.
Hebrew calendar
For Jews, time begins 5,761 years ago, a date that corresponds to 3761 B.C.
The Hebrew calendar has 12 lunar months, following the cycle of the moon around the earth. Because each lunar orbit is approximately 29 1/2 days, the 12 months total 354 days, about 11 1/4 days short of the solar year of 365 1/4 days. If there were no modifications, the months would gradually drift through the solar year, and a feast such as Passover, which must be celebrated in the spring, would slip to the winter, fall and summer before returning to the springtime.
In making the calendar more stable, the ancient Israelites received help from the Babylonians, albeit through a tragic experience. In 586 B.C., the Babylonian army invaded Israel, destroyed the Temple and took many of the country's inhabitants captive.
The Babylonian Exile was a bitter period for Israel but resulted in the adaptation of elements of the Babylonian calendar to the Hebrew measure of time. The Israelites adopted the Babylonian names for the 12 months and a method for solving their calendar conundrum of drifting months.
To compensate for the extra 11 or so days each year, an extra month of 30 days was inserted at irregular intervals.
For religious purposes, the day begins at sunset and ends the next sunset. So Rosh Hashana, a two-day holiday, begins at sunset tonight and ends at sunset Sunday.
The days of the week are numbered, Day One beginning at sunset Saturday and concluding at sunset Sunday. Only the seventh day, the Sabbath, has a proper name.
Islamic calendar
Muslims mark their time from the date when the prophet Muhammad emigrated from Mecca to Medina, referred to as the Era of Hegira, which many scholars calculate as occurring on July 16, 622.
