LEAP YEAR 'BABIES' DIVIDE THEIR BIRTHDAYS BY 4.

Byline: Harrison Sheppard Staff Writer

Susan Nash, an Encino resident and the wife of musician Graham Nash, was born on this day in 1952. So how old does that make her?

``Twelve years old,'' she responds with a laugh, adding, ``My husband likes younger women.''

Like the approximately 200,000 people in the United States and 4.1 million worldwide, Nash is a ``leaper,'' someone born on Feb. 29 in a Leap Year. And like many in this unique subculture, she celebrates her birthday once every four years, and divides her real age by four.

Today's Leap Day is particularly unique because it is the first one ever to fall in a millennium year, and the first one in 400 years in a century-ending year.

To mark the occasion, hundreds of leapers from throughout the world have flocked to tiny Anthony, Texas - the self-proclaimed Leap Year Capital of the World - which is hosting its quadrennial birthday party for leapers this week.

Graham Nash is taking time off from a reunion tour with Crosby Stills Nash & Young to perform tonight at a high school gymnasium, where he says he will probably sing ``Happy Birthday'' to his wife and the other festival participants.

For his part, Graham Nash thinks the whole Leap Year concept seems artificial.

``It's so arbitrary,'' he said. ``Just because some Roman emperor didn't like the month of February and wanted to make it shorter. It's such a man-made date.''

Actually, the Leap Year concept was adopted by Julius Caesar to compensate for a calendar year based on Earth's revolution around the sun, which takes 365 days, 5 hours, 48 minutes and about 45 seconds. Every four years, of course, a day is added to February - except in years that end in '00. In that case, the extra day is only added every 400 years.

Among other Leap Year traditions, this is supposed to be the only time when women are allowed, if not encouraged, to chase after and propose marriage to men, a custom that dates back to medieval times.

And Leap Day itself is a popular day for weddings. The Los Angeles County recorder's office had 267 couples purchase marriage licenses on the last Leap Day, Feb. 29, 1996, compared with 120 the day before.

Raenell Dawn, a Los Angeles native who co-founded The Honor Society of Leap Day Babies, lamented that calendar makers don't note that today is Leap Day - they just add the day like it's any other.

``I've spent 16 years contacting calendar companies about that,'' said Dawn, who now lives in Salem, Ore. ``I've left messages, I've written letters, I've faxed, I've e-mailed. I have not heard back from any one of them yet.''

In off years, she prefers to celebrate her birthday both on Feb. 28 and March 1, and knows other leapers who celebrate the entire month.

``Then on the 29th, when their birthday arrives, it's really time to party,'' she said.

The Associated Press contributed to this story.