Math enthusiasts celebrate Pi Day every year on March 14, to honor the mathematical constant that represents the ratio of a circle's circumference to its diameter. This year's event, however, happens just once in a century. Today, March 14, 2015, at 9:26 a.m. and 53 seconds, the date and time spelled the first 10 digits of pi: 3.141592653. Check out these photos of the "Pi Day of the Century" event at the 2015 SXSW Interactive festival in Austin, Texas. [Read full story about this year's Pi Day celebrations]

Sweet treats

Math enthusiasts all over the world celebrate Pi Day with its homophone, pie. (Credit: Tia Ghose/Live Science)

Pi(e) Day

The "Pi Day of the Century" event at the 2015 SXSW Interactive festival featured mini pies. (Credit: Tia Ghose/Live Science)

Rare event

Countdown to the "Pi Day of the Century." On March 14, 2015, at March 14, 2015, at 9:26 a.m. and 53 seconds, the date and time spelled the first 10 digits of pi. (Credit: Tia Ghose/Live Science)

Pi selfie

Live Science reporter Tia Ghose poses with a giant symbol of pi. (Credit: Tia Ghose/Live Science)

Neverending

The decimal representation of pi never ends and never repeats. (Credit: Tia Ghose/Live Science)

Circle fans

Pi is the mathematical constant that represents the ratio of a circle's circumference to its diameter. (Credit: Tia Ghose/Live Science)

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