February goes out with a zero for a date

Today marks the first time in the Gregorian Calendar that a leap-year day is being observed in a year ending in a double zero. If you are thinking, ``This is leap-year day,

Tuesday, February 29th 2000, 12:00 am

By: News On 6

Today marks the first time in the Gregorian Calendar that a leap-year day is being observed in a year ending in a double zero.

If you are thinking, ``This is leap-year day, so what?'' think again: For most Earthlings this Feb. 29 is a first.

For the first time since our current calendar spread to most of the globe, a leap-year day is being observed in a year ending in a double zero.

And, from the folks who brought you Y2K, now comes . . . well, read on.

Although it is widely believed that leap years of 366 days occur every four years without fail, there is an important exception. In century years -- the last was 1900 -- the extra day is omitted unless the year is evenly divisible by 400. There was no leap-year day in the year 1900, for example, although leap years preceded it in 1896 and followed it in 1904.

Today, Feb. 29, 2000 is the first such super-extra day to be inserted in the calendar since the Gregorian Calendar spread generally through the Western world, an interestingly agonizing process that took several centuries.

The calendar was drawn up in 1583 by a commission established by Pope Gregory XIII because the Julian Calendar created in 42 B.C. by Julius Caesar contained a small error that accumulated over the centuries into something significant.

Caesar wanted to get away from a calendar based on the moon, which by his time had gotten so skewed that winter began in September. His new calendar, the Julian, worked out by the astronomer Sosigenes, recognized that it took 365 days and a fraction for the Earth to go around the Sun.

But the Julian Calendar, which governed affairs for 1,500 years, and which incorporated the novel idea of a leap-year day to keep the calendar on track, assumed that the year was exactly 365.25 days long.

It isn't, according to Geoff Chester, public affairs officer for the U.S. Naval Observatory in Washington.

``The Earth goes around the Sun in 365.2422 days,'' he said yesterday.

That difference amounts to 11 minutes a year between the calendar and the tropical year, the time it takes the Earth to go around the Sun.

By the time of Pope Gregory XIII there was a discrepancy of 11 days, which was messing up the calculation for the date of Easter, which in turn affected other Christian days of observance.

Gregory's calendar study commission decided on a radical solution.

``They basically lopped 11 days out of the calendar. It went from Oct. 4 to Oct. 15 in 1582,'' Chester said.

Interestingly, said Chester, the Gregorian is still not exact.

``It's about 30 seconds too long,'' he said, ``and along about the year 4900 we are going to have to grapple with this problem. We will have to subtract a day. The nice thing about it is that we will have until the year 4000 to figure it out. That would be a Y4K problem.''

So how does Y2K figure into this?

Mark Nickel, spokesman for Brown University, said that now that folks have grown complacent about the Y2K problem, ``it will be interesting to see whether the calendars that are written into the software of computers everywhere are sophisticated to know there is something special today.''