REDWOOD CITY, Calif. Dust off the slide rules and recharge the calculators. Square Root Day is upon us.

The math-buffs' holiday, which only occurs nine times each century, falls on Tuesday 3/3/09 (for the mathematically challenged, three is the square root of nine).

"These days are like calendar comets, you wait and wait and wait for them, then they brighten up your day and poof they're gone," said Ron Gordon, a Redwood City teacher who started a contest meant to get people excited about the event.

The winner gets, of course, $339 for having the biggest Square Root Day event.

Gordon's daughter even set up a Facebook page one of a half-dozen or so dedicated to the holiday and hundreds of people had signed up with plans to celebrate in some way. Celebrations are as varied: Some cut root vegetables into squares, others make food in the shape of a square root symbol.

The last such day was five years ago, Feb. 2, 2004, which coincided with Groundhog Day. The next is seven years away, on April 4, 2016.