NEW YORK –– For parents debating a name for their Feb. 29 newborn, the Honor Society of Leap Year Day Babies has some suggestions: Leaporah, Leapton. Leapfrey, perhaps. Or for a Nordic touch, Leap Ericson.

With or without such bouncy names, any baby born on Tuesday will stand apart even from others with the distinction of a Leap Year Day birthday. This is the first Leap Day in 400 years to start a century.

To mark the occasion, Leap Day parties are planned across the United States and overseas, promoted by "Leaper" Web sites that have linked people whose birthdays come only once every four years.

"We get a lot of people e-mailing us who've never met anyone else born on Leap Year Day," said Raenell Dawn, co-founder of the Honor Society. "They're pretty thrilled to find they're not alone."

The most vigorously promoted party, a four-day event that got a head start Saturday, is in the small farming town of Anthony, straddling the Texas-New Mexico state line. Thousands of people, including dozens of genuine "leapers," are expected at the festivities in what has been proclaimed the Leap Year Capital of the World.

Statistically, one of every 1,461 people is a leaper. There are an estimated 200,000 in the United States and 4.1 million worldwide.

Leapers from more than 30 countries have joined the Honor Society of Leap Year Day Babies, which is approaching a membership of 1,300.

Among them is J.N. Oleap Fernando, a professor from Sri Lanka, who proposed that other parents emulate his own by giving their Leap Day babies names that reflect the special date.

Raenell Dawn, born on Leap Year Day in 1960 (and thus celebrating her 10th birthday Tuesday), endorsed this campaign on the Honor Society Web site. She also lobbies for her own favorite cause: persuading calendar publishers to designate the quadrennial Feb. 29s as Leap Year Day.

"I've written hundreds of letters, and I've never heard back from any of them," she said from her home in Salem, Ore. "You'd think they'd get the hang of it, since it's a date that celebrates the calendar."

Only a handful of mass-produced calendars designate the day, she said. One of them – a Grateful Dead calendar – adorns her home even though she doesn't listen to the band's music.

The Internet's reach has enabled leapers worldwide to feel part of a collegial, high-spirited movement. But Dawn said some elderly leapers have told her of a different era in their youth, when a Feb. 29 birthday was considered enough of an inconvenience that some parents considered registering the birth date as Feb. 28 or March 1.

Even now, some computers have trouble registering Feb. 29.

The leap year system was adopted by Julius Caesar to keep the calendar from getting out of whack and was adjusted in 1582 by Pope Gregory XII. An extra day is added every four years, except for years ending in 00 – unless the year is divisible by 400. Thus 2000 is a leap year, and so was 1600, but 1700, 1800 and 1900 were not.

Pope Gregory was not a leaper, but one of his 16th century predecessors – Pope Paul III – was. So were bandleader Jimmy Dorsey, singer Dinah Shore, football player Fran Tarkenton and hockey star Henri "Pocket Rocket" Richard.

This year, the Web of leapers is poised to identify some the first 21st century "leaplings" – newborn leapers, as defined in Raenell Dawn's "leaptionary." There's even an electronic greeting card available to mark the occasion. The message: "Jump for Joy!"