Today is March 14th, 3/14 in the normal American way of writing dates, so you'll find a lot of silliness on the web today talking about "π Day" due to the coincidental similarity with the first three digits of π (see, for example, Rhett's annual post). But, of course, this is an archaic and local convention, and not really suited to the dignity of science.
After all, the defined SI unit of time is the second, so if you're going to do things properly, you really ought to measure time in seconds (like the Qeng Ho in Vernor Vinge's brilliant A Deepness in the Sky). So, a proper celebration of the number π should fall at some power-of-ten multiple of 3.141592653589793238... There are eight of these in a calendar year (there are 31,556,736 seconds in a year, give or take), but none of them are in March.
- 1π s - This obviously occurs a bit after midnight on January 1, possibly before you finish saying "Happy New Year." Assuming you're young enough and your kids are old enough for you to be happy about being up at that hour on that date.
- 10π s - This is half a minute after midnight on January 1, around the point you're wondering "What the hell is a Lang Syne, and why would I want an old one?"
- 100π s - Just past 12:05 on January 1, maybe a good time for a silent tribute to the world's most famous transcendental number.
- 1000π s - A little bit after 12:52 on January 1. Pour an offering of flat champagne into a round glass as tribute.
- 10,000π s - 8:43am on January 1. If you're awake, celebrate by sweeping party trash from the first four celebrations into a trash can with a circular cross-section.
- 100,000π s - Around 3:16pm on January 4. The first time you could reasonably throw a "π Party" without the celebration being subsumed in another holiday.
- 1,000,000π s - About 8:40 am on February 6. This would be a really good time for a party-- it's well clear of anything else, and a time of year when people really need a pick-me-up.
- 10,000,000π s - 2:38 pm on December 29 (or 28, in a leap year). This has gone so far around that it's caught up to the winter holidays again. If you want to ostentatiously reject Christianity and all its offshoots, but still get festive in late December, this would be a good excuse.
So, there you go: if you want to properly celebrate the ratio between the circumference of a circle and its diameter, those are the correct times for your observances. None of this mid-March silliness, please. Unless you're one of those heretics who prefers τ to π, in which case, the appropriate dates are all multiplied by a factor of 2, and the proper celebration of 1,000,000τ s is on... March 14 at 5:19 pm (in a non-leap year). Hmmm...
U.S. date conventions aren't much more arbitrary or silly than base 10. I am having some trouble choosing a specific alternative, however.
I was thinking about this earlier, and to make the date actually look like pi you either have to use the European (in my experience) convention of using a period but the American convention of month/day (3.14) OR the American '/' and European day/month in July (22/7). In my, admittedly limited, experience relatively few people would actual be writing any date as pi. Besides 2pi is a much better day - it's my birthday.
And you didn't mention that one year contains about pi*10^7 seconds? What is wrong with you?
Set your clocks now for March 14 2015 at 9:26:53.