For Many, New Year’s Is Double Date Night : Religion. Various faiths observe two different calendars--and on some, the Y2K countdown has little significance.

As the clock ticks away the last seconds of December 31, Shimel Erfanian is going to party like it’s 156. Meanwhile, Maher Hathout is going to party like it’s 1420 and Ron Wolfson like it’s 5760.

In other words, there isn’t going to be much of a party at all.

To these members of the Baha’i, Islamic and Jewish faiths, respectively--and to more than a million other Southern Californians who also live by two calendars--New Year’s Eve 1999 will be merely another Friday night.

“It’s going to be a very regular evening,” said Hathout, a spokesman for the Islamic Center for Southern California, whose calendar begins with the prophet Mohammed’s flight from Mecca to Medina. “There’s nothing supernatural or metaphysical about it. All the celebrating, the popping of the champagne and dancing, we look at it as a bit silly.”

Or a bit arbitrary.

This is even clearer from a global standpoint, in which the calendar Tower of Babel rises ever higher. Worldwide, there are at least 40 different calendars calculating time in vastly different ways. They are based on everything from the sun to the moon to the swarming of sea worms--a method employed by the Kodi people of Sumba Island in eastern Indonesia.

“The Kodi people’s highest ranking official is a sort of Father Time figure,” said Janet Hoskins, a USC professor of anthropology, who wrote “The Play of Time: Kodi Perspectives on Calendars, History and Exchange” (1993, University of California Press). “His main duty is to get the timing of the planting and harvesting exactly right, which in an agricultural society like theirs is of critical importance.”

But for those who rely less upon sea worms and more upon the Western, or Gregorian, calendar, there still exist sharp differences in timekeeping--to the point that there is serious question about precisely when the millennium bash should begin.

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Purists, whose ranks include the Library of Congress and the National Institute of Standards and Technology, among others, insist the party shouldn’t start until Jan. 1, 2001. But the masses, voting with hotel reservations and party plans, say that when the cosmic tumblers hit Jan. 1, 2000, it’s time to go wild.

A review of history shows both sides probably are wrong.

According to historians, Romulus--the founder of Rome--invented the Roman Empire’s calendar in what we today would consider 750 BC. The crude calendar, however, had only 304 days and 10 months (there was no January or February). It quickly was out-of-sync with a true solar year: 365 days, 5 hours, 48 minutes, 46 seconds.

By 46 BC, Julius Caesar apparently had had enough and ordered a 365-day calendar with a leap year every four years. No major alterations were undertaken until the 6th century when Rome took another action that jeopardizes any New Year’s Eve celebrant interested in accuracy.

The church assigned the Julian Calendar a new start date--the birth of Jesus. The year chosen was AD 1.

This move, made in large part because of a Scythian monk whose name roughly translates to “Denny the Runt,” posed some problems. First, most historians now agree that Jesus was born somewhere between 7 and 3 BC. If true, that means we’re already in the third millennium.

Second, for all their aqueducts and architecture, the Romans had no concept of zero--unlike Indian and Mayan cultures. Since the first century began with AD 1, and not 0, the second century did not start until AD 101.

While a vast improvement, the Julian Calendar was still far from perfect. Three days were lost every 400 years so, and by the 16th century, the spring equinox was 10 days later than indicated on the calendar.

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To correct this, Pope Gregory XIII ordered one of the most astonishing disappearing acts of all time, eliminating the days between Oct. 4 and Oct. 14, 1582. The result was the Gregorian Calendar, but it is 26 seconds ahead of a solar year.

Thus, once again ignoring the other complications, the new year will be three hours old by the time the ball drops in Times Square.

Of course, these fine points in calendar evolution are lost upon most of us.

But many realize through their cultural or religious clashes with the Gregorian Calendar that time, and its meaning, are what we make of them.

“To us, the new millennium has no real significance,” said Erfanian, whose Baha’i faith begins its calendar in 1844, when the religion was founded by the Bab. “But we realize it may for other people.”

For Wolfson, whose Jewish calendar started with God’s creation of the Earth, Dec. 31 will be slightly more significant--as a Friday, it’s the beginning of Sabbath.

“The challenge for a lot of synagogues will be to encourage their congregants to celebrate that Friday night spiritually rather than in some other form,” said Wolfson, a vice president at the University of Judaism. “But if the hoopla around the millennium makes us pause about the significance of time, how quickly it flies, and its value and sacredness, then it might possibly serve a useful purpose.”