Chemical Industry Workers' Day is observed on the last Sunday in May in Russia, Ukraine, Belarus, and Kazakhstan. This professional holiday was established by the Presidium Decree of the Supreme Soviet of the Soviet Union on October 1, 1980, and has continued to be recognized, particularly in Ukraine where it was formalized by Presidential Decree in 1994. While it is celebrated officially in Ukraine, workers in Russia, Belarus, and Kazakhstan observe it unofficially. The holiday may vary in date depending on the Department of Chemistry at major universities, with some celebrating it on weekends in April or May. A notable tradition involves students from the Department of Chemistry at Moscow State University, who select a symbol from the periodic table to represent the holiday, a practice that began in 1966 with the symbol for Hydrogen.