In basic Math, as we all know, "pi" is equivalent to 3.14.
The date today is March 14, 2015, and today was called ''pi day'' because if we're going to change today's day with the pattern of mm/dd/yy in its numerical form, it will turn out to 31415 just like the equivalent of pi in Math. If we're going to notice the real equivalent of pi, it will be 3.1415... (and so on) so that's why today was considered as a pi day. Today is known as a pi day because our date today and the rounded value of pi are the same.
