National Mole Day
Set a timer for 6:02 on 10/23 — National Mole Day is a chemistry classroom holiday, not a food day. The date and time are a pun on Avogadro’s number, 6.02×10²³, the number of particles in one mole of a substance. It has nothing to do with Mexican mole sauce or guacamole.
About National Mole Day
History & origins
National Mole Day falls on October 23 and is unofficially observed from 6:02 a.m. to 6:02 p.m., so the stamp reads 6:02 10/23. It is a classroom and chemistry-club custom, not a government holiday.
The joke needed a home. In the early 1980s, educator Margaret Christoph wrote in The Science Teacher about celebrating the day. Maurice (Maury) Oehler, a high-school chemistry teacher in Prairie du Chien, Wisconsin, used that idea to found the National Mole Day Foundation on 15 May 1991. The foundation became a Wisconsin nonprofit in 1992, picks a yearly theme, and exists to get students enthusiastic about chemistry. Oehler died in 2020; a Mole Day exhibit stands in Prairie du Chien.
A mole (symbol mol) is an SI base unit. Since the 20 May 2019 revision of the SI, the Avogadro constant is defined as exactly 6.02214076×10²³ mol⁻¹. Classroom Mole Day still uses the rounded 6.02×10²³ that fits the clock. Amedeo Avogadro (1776–1856) did not set that modern constant; it is named in his honor.
Do not 301 this page into guacamole, mole sauce, or any food URL. TheDayOf already has `/food/national-guacamole-day-avocado/`. This day is chemistry.
Why it matters
The mole is how chemists count atoms without counting atoms. Mole Day is a silly door into a serious unit, and it gives chemistry teachers a date that students actually remember. The word collision with Mexican mole is real; say so up front so searchers are not tricked.
How to celebrate
If you teach or take chemistry, mark 6:02 a.m. or 6:02 p.m. with a mole-themed demo, puns allowed. Wear a mole (the animal) hat if that is the local joke; then do the math. Look up what a mole of water or carbon actually weighs. Check the National Mole Day Foundation theme for the year. Do not cook mole poblano for this page — that is a different mole. National Chemistry Week, run by the American Chemical Society in October, often overlaps; it is a related program, not the same day.
Facts
- Observed 6:02 a.m. to 6:02 p.m. on October 23 (6:02 10/23)
- Maurice Oehler founded the National Mole Day Foundation on 15 May 1991 in Prairie du Chien, Wisconsin
- The Avogadro constant has been defined as exactly 6.02214076×10²³ mol⁻¹ since 20 May 2019
- It is not Mexican mole sauce, not the animal (except as a classroom pun), and not guacamole
- The day is unofficial; it is not a U.S. federal holiday
Upcoming dates
- Friday, October 23, 2026
- Saturday, October 23, 2027
- Monday, October 23, 2028
- Tuesday, October 23, 2029
- Wednesday, October 23, 2030
Frequently asked questions
When is National Mole Day in 2026?
National Mole Day in 2026 falls on Friday, October 23, 2026.
What is National Mole Day?
It is an unofficial chemistry observance for the mole, the SI unit whose size is Avogadro’s number (about 6.02×10²³ particles). The date 10/23 and the time 6:02 are a visual pun. It is not a food day.
Who started National Mole Day?
High-school teacher Maurice Oehler founded the National Mole Day Foundation on 15 May 1991, after an earlier Science Teacher article by Margaret Christoph. Chemistry classes keep the custom going.
How do you celebrate National Mole Day?
Do chemistry. Hold a 6:02 a.m. or 6:02 p.m. classroom event, explain what a mole is, and enjoy the puns. Do not confuse it with mole sauce.
Is National Mole Day an official holiday?
No. It is not a U.S. federal holiday and not a UN day. It is a classroom custom. It is also not guacamole day and must not be redirected to a food page.
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