SAN FRANCISCO >> Ron Gordon would like you to take a moment or three to think about what an odd day Saturday is.

Why? Because 7/9/11 is one of only six dates this century that features three consecutive odd numbers. Next up, 9/11/13.

Gordon, a retired teacher from Redwood City, Calif., has set up a website to celebrate "Odd Day," and offers some ways to celebrate: do odds ‘n ends, root for the odds-on-favorite or watch the "Odd Couple."

Gordon has been fascinated with curious dates since some 30 years ago he noticed the date he was writing on a check: 9/9/81. That, Gordon noticed, is a Square Root Day — one in which the day and the month are the same number and, multiplied together, yield the year as it’s expressed in one or two digits.

That led Gordon to begin thinking about Odd Days, which, somewhat oddly, he has continued to do through the years.

"Like a kid, if you find a lady bug on your arm, you run around and show everyone at the picnic until the lady bug flies away," Gordon said. "This is my lady bug, and it’s not gone yet."

After 9/11/13, the next Odd Day will be 11/13/15 — and that will be it until next century. (Though we still have 4/4/16 to look forward to — the next Square Root Day.)

Gordon, 65, has turned to the web to promote the days, with his wife illustrating the websites. He has also offered cash prizes to people who do something special to commemorate them.

"The biggest piece of it is people telling people, ‘Hey, It’s Odd Day,’" Gordon said. "It creates its own interactions."

Some have acted on Gordon’s inspiration.

In Springfield, Ill., the Illinois Presbyterian senior home celebrated Odd Day on Saturday by encouraging seniors to eat their dessert before the rest of their meals and wear odd clothes, said Tom O’Fallon, the center’s executive director.

O’Fallon said he heard Gordon talking about 3/3/9, another Square Root Day, on the radio and decided to celebrate it at the senior center. The center also celebrated Odd Day on 5/7/9.

"We try and do things to make life exciting for the residents," he said.

Seniors were asked Saturday to think about odd recipes and odd relatives, and try to determine when the next Odd Day will be.

"It’s a way to use numbers to challenge your mental capabilities," O’Fallon said. "This type of thing is also good for reminiscing."