It's 123456789 Day: Mark your stopwatch

Ready! Set your watches and calendars and turn on your thinking caps. Wednesday is 123456789 Day.

At exactly 12:34:56, the time and date will be 12:34:56 7/08/09. And you can celebrate that exact moment twice in one day - with the a.m. and p.m. time. The sequence of numbers aligning with the time and date only happens once a century though.

But in Europe they'll have to wait until August for this day. People in Europe and other places list the day before the month in date abbreviations, so they will have 12:34:56 7/08/09 on Aug 7. And in some places people list the year before the month and day, so today is not 123456789 day; in those places that happened in 2007. And don't even mention military time.

Nonetheless the internet has noticed and people on Twitter and Facebook are recognizing the day. Rainn Wilson , the actor who plays Dwight from "The Office," re-tweeted about the day: "RT Shortly after 12pm on July 8, comes the moment that can be called 12:34:56 7/8/9. Happens only once a century. Too cool! (via @toni1332)."

And other Twitter users are passing along notice. There are various Facebook groups and events.

And someone made a countdown clock , so you won't miss it.