Don’t forget to set your clocks back (“spring forward, fall back”) before you go to bed Saturday night, Nov. 2. Mountain Standard Time (MST) returns at 2 a.m. Sunday, Nov. 3.
It’s also a good time to change the batteries in your smoke alarms.
Since 2007, DST has begun the second Sunday in March and ended the first Sunday in November. Only the states of Arizona (except for the Navajo Nation) and Hawaii do not use DST.
MST 2019-20 will last 126 days, slightly more than five months.
Standard time in the United States began Nov. 18, 1883, when U.S. and Canadian railroads instituted standard time in time zones, according to Wikipedia. “Before then, time of day was a local matter, and most cities and towns used some form of local solar time, maintained by some well-known clock (for example, on a church steeple or in a jeweler's window).”
Federal law established Standard time in time zones with the Standard Time Act of March 19, 1918, which also established daylight saving time, Wikipedia said.
“Daylight saving time (DST) was repealed in 1919, but standard time in time zones remained in law, with the Interstate Commerce Commission having the authority over time zone boundaries.”
With War Time Act, congress reinstated DST Feb. 9, 1942, to conserve energy resources. The Amendment to the War Time Act ended DST Sept. 30, 1945. It was re-established by the Uniform Time Act of 1967, which mandated that DST begin the last Sunday in April and end the last Sunday in October.
The 1973 energy crisis sparked by OPEC’s oil embargo led to an earlier start and later ending for DST.