There's a Reason You Can Find Pizza Deals Monday

Monday is March 14, otherwise known as 3/14, otherwise known as Pi Day, otherwise known as the day when merchants use math to sell pizzas and pies of all kinds.

• The day: It is, of course, a reference to the mathematical constant of pi, the ratio of a circle's circumference to its diameter. It gets rounded to 3.14, and the link to March 14 has been a mathematical holiday of sorts since 1988, according to a backgrounder by ABC News.
• The deals: USA Today has a pretty thorough roundup of food deals (often pizza deals for $3.14) at 7-Eleven, BJ's, Dominos, Chuck-E-Cheese, Cici's, and on and on.

• The deals, II: Tech site CNET has a similar roundup, one that includes non-pizza-pies from the likes of Boston Market, Goldbelly, Grand Traverse Pie Company, and Marie Callender's.
• The record: The first digits of pi are 3.14159265359, though a Google employee calculated it to 31 trillion digits a few years ago. However, the mark was more than doubled last year by the University of Applied Sciences in Switzerland and verified by Guinness World Records. It took their supercomputer 108 days to reach 62.8 trillion digits, per the Guardian.

(More Pi Day stories.)