Depends
on Date Format
People in countries that write their dates in the date/ month
format celebrate Pi Approximation or Casual Pi Day on 22 July
or 22/7. On the other hand, those who write their date in
month/ date format celebrate Pi Day on March 14 (3/14 or 3-14)
because the first three digits of the date correspond to the
first three digits of pi - 3.14.
Move to
Replace Pi
In recent years, some mathematicians and physicists have argued
for the replacement of the π by tau and to celebrate Tau Day
on June 28 instead of celebrating Pi Day or Pi Approximation
Day.
