Technical Specifications & Standards
Official chronometric properties, ISO standards, and international database registry identifiers for Mountain Standard Time:
Daylight Saving Time (DST) Transitions
⬆️ Spring Forward (Clocks Advance)
Second Sunday in March at 02:00 AM (Clocks advance to MDT, except in Arizona)
⬇️ Fall Back (Clocks Return)
First Sunday in November at 02:00 AM (Clocks return to MST)
Observing Jurisdictions & Subdivisions
3 Sovereign NationsSovereign nations, administrative subdivisions, and regional territories officially operating under MST:
Regional Subdivisions & Territory Details
Financial Markets & Trading Hours
Acts as the operational link between Midwest manufacturing desks and West Coast technology offices.
Local Hours: 08:30 - 16:30 MST
UTC Window: 16:00 - 00:00 UTC
Local Hours: 08:30 - 16:30 MST
UTC Window: 16:00 - 00:00 UTC
Major Cities in MST
Primary metropolitan centers and financial hubs observing this time zone:
Adoption History & Astronomical Facts
Year Established: 1883
Established along the 105th meridian west of Greenwich, passing right through Denver. Because the meridian sits almost exactly one mile above sea level in Colorado, the city was nicknamed the Mile High City.
Most of Arizona refuses to observe daylight saving time to avoid adding another hour of daylight to 110-degree summer afternoons. But the Navajo Nation in northeastern Arizona does observe daylight saving, while the Hopi reservation surrounded by Navajo land does not.
Frequently Asked Questions about MST
What does MST stand for?
MST stands for Mountain Standard Time, seven hours behind Coordinated Universal Time (UTC-7).
Does Phoenix, Arizona change its clocks for daylight saving?
No. Aside from the Navajo reservation, Arizona remains on MST (UTC-7) all twelve months of the year.
What is the time difference between Denver and New York?
Denver is two hours behind New York. When it is noon in Manhattan, it is 10:00 AM in Denver.