OK, caught me with too little coffee. My main point is that this is not an "international" pi day because seeing it as 3/14 is not necessarily a majority point of view. I was also trying to remember what the months were in Julian, which would have been in force outside of Catholic countries at the time. If you want it totally nerded out, a pi day existed best when there was a leap month in the old roman calendar, in which 31 March would have been 31st day of 4th month, except it wouldn't have existed unless the Romans were using decimal notation. Then it would have been more special by being every four years.