Mole Day is celebrated every October 23 from 06:02 to 18:02.
Mole Day was first mentioned in an article in The Science Teacher in 1980-something.
Inspired by this article, high school chemistry teacher Maurice Oehler, from Prairie du Chien, Wisconsin, founded the National Mole Day Foundation (NMDF) on May 15, 1991 to promote that chemistry is fun!
A mole is a measurement unit used in chemistry with a very long explanation.
So if you are interested just click on the word for a wikipedia explanation.
The time was picked as a number play on Avogadro’s Number (6.02 x 1023). And that is why this day is not a whole day but from 06:02 to 18:02.