It's Odd Day, 11/13/15

SAN FRANCISCO - Today's an odd day, because it's Odd Day. When written as 11/13/15, the date is made up entirely of sequential odd numbers.

Those in awe of this oddity might want to pause to ponder at 21 seconds after 5:19 p.m.

That's when the date and time (if you're working in military time) would be written 11/13/15 17:19:21.

You can't get odder than that.

Pay attention, as there won't be a repeat for quite awhile. Sequential odd days only hit six times in a century and this is the last one for the 21st.

The calendrical odd-man-out won't come again for 90 years, when Jan. 3, 2105 rolls around. Then it will be 1/3/5.

The non-holiday is most fervently celebrated by math aficionado and retired teacher Ron Gordon, who lives in Redwood City, Calif.

He's established a contest for the most people involved in the Oddest Parade of Odd Day Characters. The winners will receive the date, in dollars — $1,113.15.

Odd Day is a lot quieter than its numerical cousin, Pi Day. That's celebrated on March 14, especially at 1:59, when it’s 314159.

“We’re like  Pi Day without the dessert,” said Gordon, a man who keeps his tongue firmly in his cheek.

Pi Day in less than 30 seconds

Gordon has some suggestions as to how to celebrate Odd Day: do some odds 'n ends, give a friend a high-five, root for the odds-on-favorite, watch the Odd Couple, find missing odd socks and beat the odds.