Time Zone History

Denver time zone history

Standard time has stayed at UTC−7 since 1883, tied second-longest run among the 148 zones with no change of standard time since 1970. Denver left local mean time (UTC−6:59:56) in 1883, tied for the earliest switch among the 11 zones on UTC−7 standard time with local mean time in the record. Clocks have been changed 114 times since 1970, tied for the most among the 12 zones on UTC−7 standard time.

UTC−7

Standard time is UTC−7 (MDT/MST); clocks go forward to UTC−6 on the second Sunday in March and back on the first Sunday in November.

Covers: Mountain time, most areas · tz database name America/Denver

Convert a time from Denver

Summer time in every year since 1970

UTC−7: today’s standard timeUTC−6:59:56: 4 seconds ahead of today’s standard timeUTC−6: 1 hour ahead of today’s standard timeUTC−7: today’s standard timeUTC−6:59:56: 4 seconds ahead oftoday’s standard timeUTC−6: 1 hour ahead of today’sstandard time

How to read this chart

Before 1970

187018901910193019501970187019101950
JanFebMarAprMayJunJulAugSepOctNovDec1970198019902000201020202028JFMAMJJASOND1970198019902000201020202028

Standard time changes

DateChangeNew standard timeClock label
Before 1970
November 18, 1883Local mean time (UTC−6:59:56) replacedUTC−7MST

Daylight saving periods

YearsClocks go forwardClocks go backShift and labels
1918–1920last Sunday in March, 02:00last Sunday in October, 02:001 hour, MST to MDT
1921March 27May 221 hour, MST to MDT
1942February 9not that year1 hour, MST to MWT
1945not that yearSeptember 301 hour
1965–1973last Sunday in April, 02:00last Sunday in October, 02:001 hour, MST to MDT

Since 1970: the periods shared by 5 of 29 zones, listed on the United States page.

Clock changes in 2026, 2027 and 2028

The clocks go forward 1 hour (MST to MDT) on March 8, 2026, March 14, 2027 and March 12, 2028 at 02:00 and back 1 hour (MDT to MST) on November 1, 2026, November 7, 2027 and November 5, 2028 at 02:00, local time.

Also on UTC−7

Ciudad Juárez (Mexico), Phoenix (United States), Boise (United States), Hermosillo (Mexico), Vancouver (Canada), Mazatlan (Mexico), Dawson Creek (Canada), Fort Nelson (Canada), Whitehorse (Canada) and Cambridge Bay (Canada) (nearest first; 1 more on the list of offsets).

Clocks next door since 1970

  • New Salem, North Dakota (841 km): same time except 8,467 days in 2003–2026; 1 hour ahead today.
  • Center, North Dakota (872 km): usually 1 hour ahead; different on 8,336 days in 1970–2026.
  • Beulah, North Dakota (876 km): same time except 5,898 days in 2010–2026; 1 hour ahead today.
  • Ciudad Juárez (Mexico) (900 km): same time except 5,334 days in 1970–1998, 2001, 2007–2009 and 2022.
  • Phoenix (943 km): usually 1 hour behind; different on 8,613 days in 1970–2026; same time today.