Decree time refers to the changes introduced to the Soviet Union time system by a Sovnarkom decree of 16 June 1930. By this decree, all clocks in the Soviet Union were permanently shifted one hour ahead at 00:00 on 21 June 1930 everywhere in the Soviet Union. Applicability of this decree was further extended by two other decrees in 1930 and 1931. The practice was further extended, and its legal basis was amended, in 1980.