Mole Day is an unofficial holiday celebrated among chemists and chemistry students on October 23, between 6:02 AM and 6:02 PM, making the date 6:02 10/23 in the American style of writing dates. The time and date are derived from Avogadro's number, which is approximately 6.02×1023, defining the number of particles (atoms or molecules) in one mole of substance, one of the seven base SI units.
Mole Day originated in an article in The Science Teacher in the early 1980s. Inspired by this article, Maurice Oehler, now a retired high school chemistry teacher from Prairie du Chien, Wisconsin, founded the National Mole Day Foundation (NMDF) on May 15, 1991.
Many high schools around the United States, South Africa, Australia and in Canada celebrate Mole Day as a way to get their students interested in chemistry, with various activities often related to chemistry or moles.
|1991||The Mole The Merrier|
|1992||Go For The Mole|
|1993||Mole Out The Barrrel|
|1994||An Ace in The Mole|
|1997||We Dig Chemistry|
|1998||Ride the Molercoaster|
|1999||It's A MOLE World|
|2000||Celebrate the Molennium|
|2003||Rock "n" Mole|
|2004||Pi a la MOLE|
|2007||Secret Agent Double Mole Seven in Moles are Forever|
|2008||Remember the Alamole|
|2010||Moles of the Caribbean|
|2011||Moles of the Round Table|
Alternate observances 
- Some schools celebrate "Mole Week" around October 23.
- The American Chemical Society sponsors National Chemistry Week, which occurs from the Sunday through Saturday during October in which the 23rd falls. This makes Mole Day an integral part of National Chemistry Week.
See also 
- This Week in Chemical History, American Chemical Society, retrieved 2010-02-14
- "National Chemistry Week Celebrates 20 Years", Chemical & Engineering News 85 (51), December 17, 2007, retrieved 2010-02-14
- "Chemistry In The Spotlight", Chemical & Engineering News 88 (50), December 13, 2010, retrieved 2010-02-14
- "History of National Mole Day Foundation, Inc.". moleday.org.
- "National Mole Day Foundation, INC". Moleday.org. 2011-11-18. Retrieved 2012-10-23.
- "Chemical club wins national recognition)". Central Michigan Life. 27 September 2004. Retrieved October 8, 2012.