**A once-in-a-lifetime sequential time representing the first 10 digits of pi will occur on March 14, 2015.**

A sequential time will occur on 3/14/15 at 9:26:53 a.m. and 9:26:53 p.m. following the first 10 digits of the mathematical constant pi; 3.141592653. A date-time alignment such as this occurs only one day every century and also lands on Albert Einstein’s birthday.

Pi, often represented by the Greek letter “π,” is the ratio of a circle’s circumference to its diameter. Pi is known as an irrational number because it can’t be represented as a fraction and can’t be calculated by dividing two integers. In decimal form, pi continues indefinitely with no repeating pattern in the number, making it truly unique.

Pi Day is a holiday celebrating the mathematical constant which occurs annually on March 14. The day was chosen due to the fact that the abbreviated date, 3/14, represents the first three digits of pi. However Pi Day in 2015 is an event that comes around just one day ever 100 years. This once in a century sequential time alignment representing the first 10 digits of pi, 3.141592653, will occur on 3/14/15 at 9:26:53 a.m. and 9:26:53 p.m.

Some countries which use the day-month-year date format choose to celebrate Pi Approximation Day on July 22, as the fraction 22/7 is a common approximation of pi. In 2014, some people chose to celebrate pi for the entire month of March, as the month-year date format, 3/14, represented pi.

Pi is used regularly by NASA scientists for a wide variety of purposes. Mission scientists operating Mars rovers Curiosity and Opportunity use pi to calculate the distance the rovers’ wheels travel each day. Pi is also used to calculate the volume of the subsurface ocean on Jupiter’s moon Europa. Mission scientists frequently use pi to determine the amount of time it will take a spacecraft to complete an orbit at a given altitude of other worlds in the solar system.

Want to find out first hand how NASA uses pi? Take NASA’s Pi Day Challenge.