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Pi Day
March 14
March 14 marks Pi Day, an annual celebration of the mathematical sign pi. March 14 was selected because the numerical date (3.14) represents the first three digits of pi, and it also happens to be Albert Einstein’s birthday.
Pi is a number that defines what a circle is. It’s the ratio of a circle’s circumference to its diameter, and it’s the same for every circle: 3.141592 followed by a string of over 22 trillion other digits. That unwieldy and enigmatic number is what makes a circle, a circle.
