Pi Day is a celebration commemorating the mathematical constant π (pi). Pi Day is observed on March 14, since 3, 1, and 4 are the first three significant digits of π in decimal form.
The earliest known official or large-scale celebration of Pi Day in USA was organized by Larry Shaw in 1988 at the San Francisco Exploratorium, where Shaw worked as a physicist.
On March 12, 2009, the U.S. House of Representatives passed a non-binding resolution (HRES 224), recognizing March 14, 2009 as National Pi Day.
In the year 2015, Pi Day will have special significance on 3/14/15 at 9:26:53 a.m. and p.m., with the date and time representing the first 10 digits of π (3.141592653). However, some say that 9:26:54 a.m. and p.m. on 3/14/15 are more accurate because of the 11th digit of π is 5, which would cause the 10th digit to round up to 4.
I came to know about this information through an article published in Bombay Times on 14 March 2015.
March 14 is birthday of Albert Einstein also.