article_snippet: (CNN)Pi Day is going to be extra special this year, as 2015 stretches the symbolic
article_snippet: And if you mark pi at 9:26.53 in the morning or night, you're just a little more in line with the celebrated irrational number that never ends.
article_snippet: To 31 decimal places, pi is 3.1415926535897932384626433832795.
article_snippet: A few more tidbits about pi and Pi Day: .
article_snippet: Pi is the ratio of the circumference of a circle to its diameter.
article_snippet: Pi is essential in architecture and construction and was used frequently by early astronomers.
article_snippet: Pi has been known for about 4,000 years, but it started to be called by the Greek letter only in the 1700s.
article_snippet: The origin of Pi Day .
article_snippet: Pi Day is also Albert Einstein's birthday.
article_snippet: For more about pi, visit www.piday.org.
highlights_snippet: Pi  Day is celebrated March 14 in honor of the famed irrational number .
  