400 students celebrate Pi Day 2015 at St. Anthony Village High School

More than 400 students at St. Anthony Village High School are celebrating Pi Day, a day early, with special t-shirts and classroom fun.

Pi Day is celebrated worldwide on March 14 (3/14) in observance of the Greek letter Pi, which is used in mathematics to represent a constant -- the ratio of the circumference of a circle to its diameter --which is approximately 3.14.

Pi Day 2015 is an especially unique date, because if you calculate it another two digits past the decimal point, it comes out to 3.1415.