1918    The U.S. Congress establishes time zones and approves daylight saving time.

1918    Daylight saving time goes into effect in the United States for the first time.

1942    Year-round Daylight saving time is re-instated in the United States as a wartime measure to help conserve energy resources.

1974    In response to the 1973 energy crisis, daylight saving time commences nearly four months early in the United States.

1981    Daylight saving time is introduced in the USSR.