Mole Day (23 October)

On his 14 March 2009 page (p292) “Didapper” wrote that mathematicians know 14 March as Pi Day, because 3.14 is the three-digit approximation of pi.

In a similar vein, 23 October is celebrated among chemists in North America as Mole Day. The day officially begins at 6.02am, making the time and date 6.02 10/23 in the US style of writing dates. This precise moment is derived from the Avogadro constant, 6.02x10²³, which is the number of atoms or molecules in one mole of a substance.

Mole Day originated in the early 1980s in an article in a US magazine for high school science teachers. The aim is to encourage an interest in chemistry through activities related to chemistry in general or to moles in particular.  

The date has even been taken up by the American Chemical Society, which sponsors an annual National Chemistry Week during the Sunday to Saturday period in which 23 October falls.

Apparently some rebel schools celebrate Mole Day on either 6 February or 2 June, both of which can be represented as 6.02. They presumably start their festivities at 10.23am.