Montana is currently in Standard Time, but on Sunday, March 10, Daylight Saving Time will be implemented and clocks will “spring forward” one hour.
The change occurs at 2 a.m. Sunday.
The NASA website explains the origin of Daylight Saving Time:
In 1966, President Lyndon Johnson signed an act into law whereby Daylight Saving Time begins on the last Sunday of April and ends on the last Sunday of October each year. However, any State can opt out of Daylight Saving Time by passing a State law.
Hawaii does not observe Daylight Saving Time and neither does Arizona (although the Navajo Nation, in northeastern Arizona, does). For many years, most of Indiana did not observe Daylight Saving Time with the exception of 10 counties. Beginning in 2006, all of Indiana now observes Daylight Saving Time.
Until 2007, the return to Standard Time occurred on the last Sunday of October, but in 2005, Congress changed the date to the first Sunday of November.
The next “fall back” will occur Sunday, November 3, 2019.