National mole day
National Mole Day is 23 October, from 6:02 a.m. to 6:02 p.m. Chemistry classes mark Avogadro’s number, written as 6.02 × 10^23. It is a classroom observance, not a public holiday.
what national day is it today
What national day is it today, on this page, means: is the civil date 23 October, and are you inside the 6:02-to-6:02 window the name plays on? On 3 September 2026 that October date has not arrived. The next Mole Day is Friday, 23 October 2026. After that it returns on Saturday, 23 October 2027. The square does not move to a nearby Monday. If 23 October is a Sunday, unofficial Mole Day is still Sunday.
The American date 10/23 plus the time 6:02 is a mnemonic for 6.02 × 10^23, the order of magnitude students meet as Avogadro’s number: the number of particles in one mole of a substance. The mole is an SI base unit. The 2019 redefinition fixed the Avogadro constant at an exact value near that familiar 6.02 × 10^23. The day still uses the classroom rounding, because that is the joke the clock can tell.
Maurice Oehler, a chemistry teacher in Prairie du Chien, Wisconsin, founded the National Mole Day Foundation on 15 May 1991 after earlier classroom celebrations, including work described by educator Margaret Christoph. The Foundation picks a yearly theme and exists to get students enthusiastic about chemistry. It does not close the courthouse.
A twelve-hour science joke
The printed day is 23 October. The printed hours are 6:02 a.m. to 6:02 p.m. A school that starts after 6:02 still keeps the date. A club that meets at lunch is still on Mole Day. The overnight hours on either side are ordinary clock time, not a second holiday. National Chemistry Week, run by the American Chemical Society, is the Sunday-through-Saturday span that contains 23 October. In 2026 that week is 18–24 October. Mole Day sits inside it. The week is not a license to treat the whole month as the day.
Activities are local: mole-themed problems, puns, food that can be counted in moles, or a display about Amedeo Avogadro. None of that is required. A lab that has a test on 23 October is still a lab with a test. The unofficial day does not cancel the syllabus.
Lock 23 October. Do not slide it to Friday for convenience. If you want the full mnemonic, mark 6:02 a.m. through 6:02 p.m. on that date. Treat the animal mole and Mexican mole sauce as other words. This page is the chemistry unit.
If you need a public holiday, look at a legal calendar. This is not one. A mole is an amount. A garden mole is a mammal. If your poster has whiskers and no 10^23, you packed the wrong animal.
Questions and answers
- When is National Mole Day?
- Every 23 October, commonly from 6:02 a.m. to 6:02 p.m. In 2026 that Friday is 23 October; in 2027 it is Saturday, 23 October.
- Is Mole Day a day off?
- No. It is an unofficial chemistry observance. Schools and offices keep ordinary hours unless they plan their own event.
- Why 6:02 and 10/23?
- Together they mimic 6.02 × 10^23, the classroom form of Avogadro’s number used to define a mole of particles.
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