If you're interested in being even more precise, 9.26.53 on Saturday morning yields even more numbers: the expression of date and time matches the irrational number to ten digits: 3.14.15, 9.26.53.
American physician Larry Shaw celebrated the first Pi Day in 1988 with colleagues at the San Francisco Exploratorium, after he noticed that according to the US calendar, March 15 and 1.59.26 allowed Pi to be expressed to five decimal places.
These who choose to celebrate Pi Day on March 15 each year have to choose between the 12 hour and 24 hour clocks. According to purists, 1.59.26 in the early hours of the morning is the true time for Pi, since marking the event in the afternoon would give a time of 13.59.26, and potentially throw circumferences into a spin.
After Saturday's event, the numerically inclined can look forward to 4.4.2016, next year's Square Root Day.