International Mole Day is an unofficial holiday celebrated annually on October 23 from 6:02 a.m. to 6:02 p.m. to honor Avogadro's Number (6.02 × 10²³), the fundamental measuring unit of a mole in chemistry.
 

Core Significance

• Date and Time: The date (10/23) and time (6:02) directly mirror Avogadro’s constant of 6.02 × 10²³ particles (atoms or molecules) per mole.
• Origin: Inspired by an 1980s magazine article by educator Margaret Christoph, Maurice Oehler founded the National Mole Day Foundation on May 15, 1991, to spark curiosity in chemistry.
• Amedeo Avogadro: The day pays tribute to the Italian scientist (1776–1858) who first hypothesized that equal volumes of gases at the same temperature and pressure contain an equal number of molecules.