day (pi is 3.14 to the nearest hundredth) is not universal. It appears that the US is one of only a few countries that uses the month/day/year format. However, as with most things, the origin of the difference is not easily determined as this discussion shows. This Wiki shows where in the world the different formats are used. And yet we typically say the 4th of July which is a nod to the British way of doing things which seems a little odd since it was the British from whom we gained independence on July 4th, or was it the 4th of July.
Pi is much more interesting. It is a constant, irrational number that is a ratio between the length of the circumference of any circle and its diameter. The circumference of any circle is just over 4 times its diameter. In itsfraction form 22/7, 22 is the circumference and 7 is the diameter. There are so many lists of facts about Pi, from 5 to 50 on-line, and it's probably the most blogged about mathematical symbol in the history of maths. It's also probably one of the most poorly taught concepts in school as it is usually presented as a long, long number, often graphically represented on the walls of school hallways and yet seldom explored for what it really is. Here's a neat Pi Facts blog site that lists just 5 facts but they are really good especially the fact about the mirror image of 3,14 being PIE.Here is a list of 50 facts; probably TMI.
In a lecture I gave last October I raised the issue of there being no Pi Day in the UK. Later, someone in the audience emailed me to say there was, in fact, 12 of them this year, the third day of each month could be a Pi Day (1/3/14, 2/3/14, 3/3/14, 4/3/14, 5/3/14, 6/3/14, 7/3/14, 8/3/14, 9/3/14, 10/3/14, 11/3/14 and 12/3/14.).
Being both a British and a US citizen I have always found it difficult to remember which way to write it. Luckily I was born on Dec. 19th so 12/1946 always works in the US.