WHOSE MILLENNIUM IS IT? CALENDARS VARY AMONG NATIONS

If people in non-Western cultures aren't quite as excited as the rest of us as the millennium clock counts down to 2000, one reason might be the new year will be 4637 for billions of Chinese and 1488 for many Muslims around the world.

The Gregorian calendar, in existence since 1582, has become the standard for international communication and commerce. In that sense, the whole world is celebrating a new millennium, but the same religious basis for the date in the Gregorian calendar Christ's birth does not have the same significance to much of the world's population.

The Hebrew calendar dates from 3,760 years and 3 months before the beginning of the Christian era. The date is supposed to be the moment Creation began. Hindus have numerous gods and calendars. For some, this is the year 1921. For others, 2056. In Islam, the calendar dates from the year of Muhammad's flight from Mecca to Medina, an event called the hegira. Many Iranians observe yet a different dating system that makes this the year 1378.

Buddhists date their calendar from the birthday of the Buddha in 480 B.C. In the Chinese calendar, years are divided into cycles of 60. The year 2000 is the 17th year of the 78th cycle, and the years in each cycle are associated with one of 12 animals. 2000 will be the year of the dragon.

Instead of B.C. and A.D., some non-Christians use the terms B.C.E (before Christian era) and C.E. (Christian era).Why the Gregorian calendar became so widely accepted appears to be a matter of business."It's primarily economic and trade, the convenience of trade and dating that that the calendar was used," says Dr. Frank Nickell, director of the Center for Regional History at Southeast."We're talking years for some of those connections to be made and sometimes years for them to make the trip. "It was the fact that Western Europe faced the Atlantic trade connections that tied it together," Nickell said.

The Gregorian calendar was devised in 1582 after more than 1,500 years when the West used the calendar named for Julius Caesar. Caesar had corrected miscalculations in the Roman calendar that resulted in an accumulated error of three months, putting autumn in July, the month now named for Caesar.

To straighten things out, Caesar decreed the year 46 B.C. would last 445 days, a period that came to be known as the "year of confusion."Alas, Caesar wasn't perfect. The Julian year was still 11 minutes and 13 seconds longer than the solar year, so by 1580 the equinoxes were occurring 10 days earlier than they were supposed to.

A Jesuit mathematician named Christopher Clavius devised the Gregorian calendar at the instigation of Pope Gregory using new astronomical information. Clavius deduced that a year was shorter in 1582 than it was in 45 B.C. -- 365.2419 days compared to 365.2422 days. In part, his solution required dropping the 10 days from October 1582, the month with the least holy days.

To maintain the calendar's accuracy, the pope also ordained that no century year could be a leap year unless the date is divisible by 400.

Clavius' calculations were so precise that an extra full day won't have to be added to the calendar until the year 4517.

Because the Orthodox Church viewed the Gregorian calendar as an imposition by Rome, the calendar was not accepted in England until 1751 and not in Russia until the Bolshevik revolution in 1917.