Den første fejring af Pi-dag skete på [[San Francisco Exploratorium]] i [[1988]], hvor [[fysiker]]en Larry Shaw lavede et arrangement med flere elever og ansatte, hvor de spiste tærte (engelsk: ''pie'') og gik rundt i cirkler.<ref name="sanfran">{{cite web
  | url = http://articles.sfgate.com/2009-03-11/entertainment/17211858_1_pi-day-pi-shrine-einstein-s-birthday  | title = Any way you slice it, pi's transcendental  | last = Berton  | first = Justin  | date = 11. marts 2009  | work = [[San Francisco Chronicle]]  | access-date=18. marts 2011}}</ref><ref name="ABC – Science – 10 Mar 2011 – infinite appeal of pi">{{Cite web |url=http://www.abc.net.au/science/articles/2011/03/10/3158045.htm?site=science/opinion |title=The infinite appeal of pi |last=Borwein |first=Jonathan  |author-link=Jonathan Borwein |date=10. marts 2011 |publisher=[[Australian Broadcasting Corporation]] |access-date=13. marts 2011}}</ref><ref name="fresnobee">{{cite news |url=http://apollotutoring.com/pi_day.pdf |title=A place where learning pi is a piece of cake |last=Apollo |first=Adrian |date=10. marts 2007 |newspaper=[[The Fresno Bee]] |access-date= 6. juli 2020 |archive-date=28. februar 2014 |archive-url=https://web.archive.org/web/20140228131924/http://apollotutoring.com/pi_day.pdf |url-status=dead }}</ref>
Matematik