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Mountain Time • MST / MDT • Arizona & Boundary Map

Mountain Time Zone Map

See exactly where Mountain Time is used and where it meets Central and Pacific Time. Explore both U.S. Mountain Time boundaries, inspect split states, compare Phoenix with Denver and choose any date to see whether a location uses MST (UTC−07:00), MDT (UTC−06:00) or a year-round local rule.

Central–Mountain boundary Mountain–Pacific boundary Arizona DST difference Live MST / MDT Any-date view Print & download
Loading Mountain Time geography · two boundaries + Arizona view
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Interactive Mountain Time Zone map A focused map of Mountain Time in the United States and nearby North America. Mountain Time is highlighted between Central and Pacific Time, with searchable cities, split-state boundary context, Arizona DST differences and date-aware MST or MDT labels.
Mountain Time geometry is shown with date-aware IANA rules. U.S. legal boundaries are checked against 49 CFR §§ 71.7–71.9; interactive polygons are cartographic reference geometry, not a legal survey. Sources & methodology · Need rules instead? Open the Mountain Time Zone guide

A Mountain Time Map Built Around Boundaries & DST Exceptions

Mountain Time sits between two major U.S. boundaries, while Arizona creates one of the most important daylight-saving exceptions on any American time-zone map.

See Mountain vs CentralFollow the eastern edge through North Dakota, South Dakota, Nebraska, Kansas and far-west Texas.
See Mountain vs PacificInspect the western edge through Idaho, Oregon and the federal West Wendover exception in Nevada.
Understand Arizona by dateSee Phoenix remain on MST while Denver changes between MST and MDT in locations that observe daylight saving time.
Inspect split statesJump directly to states where a one-color map hides county-level or city-level time-zone geography.

MST vs MDT on the Mountain Time Zone Map

Mountain Time is the umbrella zone; MST and MDT describe different clock rules. Mountain Standard Time is UTC−07:00. Mountain Daylight Time is UTC−06:00 in participating locations during daylight saving time.

Arizona makes this distinction especially important. Most of Arizona stays on MST year-round, while Denver and most other U.S. Mountain locations advance to MDT during the federal DST season. The Navajo Indian Reservation is an Arizona exception that does observe DST.

MST · UTC−07:00Mountain Standard Time is the standard-time label and is also used year-round across most of Arizona.
MDT · UTC−06:00Mountain Daylight Time is used during daylight saving time in participating Mountain locations such as Denver.
2026 U.S. DST windowDaylight saving time runs from March 8 to November 1, 2026 in participating U.S. locations; most of Arizona does not switch.

Mountain Time Boundary States & Exceptions

Mountain Time is shaped by two federal boundaries plus a major daylight-saving exception in Arizona. These are the places where a state-level color alone can be misleading.

Full U.S. map →
StateMountain Time AreaNeighbor Zone / ExceptionBoundary ContextDetailed MapTime Zone Guide

How to Read the Mountain Time Zone Map

Six details explain why Mountain Time is more complicated than a simple UTC−07 or UTC−06 label.

01 · Two Edges

Mountain Sits Between Central and Pacific

49 CFR § 71.8 defines the U.S. Mountain zone as the area west of the Central–Mountain boundary and east of the Mountain–Pacific boundary.

02 · Arizona

Most of Arizona Stays on MST

Most of Arizona does not observe daylight saving time, so Phoenix remains at UTC−07:00 while many other Mountain locations switch to MDT.

03 · Navajo

Arizona Has a DST Exception

The Navajo Indian Reservation observes daylight saving time. That makes Arizona a location where zone identity and seasonal rules cannot be reduced to one statewide clock rule.

04 · Split States

Follow Counties, Rivers and City Limits

The federal boundaries use county lines, state lines, rivers and specific municipal boundaries rather than a single longitude.

05 · Same Offset

MST Can Match Pacific Daylight Time

In summer, Phoenix at MST UTC−07:00 can share the same numeric offset as California on PDT without Phoenix becoming part of the Pacific Time Zone.

06 · Legal Detail

Murdo and West Wendover Matter

Federal rules explicitly name Murdo, South Dakota as Central Time on the eastern boundary and route the western boundary around West Wendover, Nevada.

Explore Mountain Time Boundaries in More Detail

Open the U.S. overview, compare the neighboring zones or zoom into the state maps where Mountain Time geography becomes most useful.

Open U.S. Time Zone Map →
Parent mapUnited StatesAll U.S. zones and boundary context Neighbor zoneCentral TimeThe eastern side of the Central–Mountain line Neighbor zonePacific TimeThe western side of the Mountain–Pacific line DST exceptionArizonaMST year-round in most of the state Split stateNebraskaCentral / Mountain boundary detail Split stateSouth DakotaCentral / Mountain boundary and Murdo Split stateIdahoMountain / Pacific boundary detail Map directoryAll Time Zone MapsWorld, regional, zone, state and country maps

Where the Central–Mountain Boundary Runs

49 CFR § 71.7 traces the eastern edge of Mountain Time from the U.S.–Canada border through North Dakota, South Dakota, Nebraska and Kansas, then along Oklahoma, Texas and New Mexico. Municipalities directly on this boundary are assigned to Mountain Standard Time, except Murdo, South Dakota, which is specifically assigned to Central Standard Time.

North Dakota boundary detail South Dakota & Murdo detail Nebraska boundary detail Central Time side of the boundary

Mountain Time State Map Shortcuts

Use these focused maps for state-scale geography, Arizona’s DST exception and both Mountain Time boundaries.

Exception mapArizonaPhoenix, MST year-round and DST differences Detailed mapNorth DakotaCentral / Mountain boundary detail Detailed mapKansasWestern Mountain counties and Central majority Detailed mapOregonPacific majority and Mountain exception Detailed mapIdahoMountain / Pacific split around the Salmon River Broader mapUnited StatesCompare Mountain with every U.S. time zone Adjacent zoneCentral TimeFollow the eastern boundary from the other side Adjacent zonePacific TimeFollow the western boundary from the other side
Printable • SVG • PNG

Zoom to the Central–Mountain boundary, Mountain–Pacific boundary or Arizona, choose the date you need, then print the focused map or save it as SVG or PNG.

For reference use only. U.S. legal time-zone boundaries are governed by federal law and may change through rulemaking; interactive cartographic polygons are not a legal survey.

Mountain Time Map vs Mountain Time Guide

Use this page when geography is the question. It shows where Mountain Time is used, both U.S. boundaries, split states and why Arizona can behave differently from Denver on the same date.

Use the Mountain Time Zone guide for definitions, places, IANA examples and seasonal rules. Use MST Time Now or MDT Time Now when the live abbreviation itself is your task.

Mountain Time ZoneU.S. Time Zones

Why Phoenix and Denver Can Show Different Times

In winter, Phoenix and Denver are normally both on MST at UTC−07:00. During U.S. daylight saving time, Denver advances to MDT at UTC−06:00 while most of Arizona remains on MST at UTC−07:00. Phoenix can therefore match Pacific Daylight Time numerically without becoming part of the Pacific Time Zone.

Arizona Time Zone Map Central Time Zone Map Pacific Time Zone Map Time Zone Chart

Mountain Time in 2026: MST, MDT & Arizona

The Mountain Time geography stays recognizable while participating locations change seasonal offset and most of Arizona does not.

Participating U.S. Mountain locations · 2026March 8 → November 1

Denver and other participating locations use daylight saving time during this federal 2026 window.

Denver seasonal patternMST −07 → MDT −06

Denver advances one hour during daylight saving time and returns to MST when standard time resumes.

Most of ArizonaMST · UTC−07:00 year-round

Phoenix does not switch to MDT; the Navajo Indian Reservation is an Arizona exception that observes DST.

Sources & Methodology

CalendarHours separates four data questions: legal U.S. boundary description, base geography, IANA time-zone rules and interactive boundary geometry. The official U.S. Mountain zone and its two principal boundaries are checked against 49 CFR §§ 71.7–71.9 and U.S. Department of Transportation time-zone oversight materials.

Date-aware abbreviations and UTC offsets use IANA time-zone rules available through the browser. The current database baseline is tzdb 2026c, released July 8, 2026. Interactive time-zone polygons use the timezone-boundary-builder 2026c generation based on current IANA rules and updated OpenStreetMap inputs. NIST is used for U.S. daylight-saving rules, including the Arizona and Navajo exception.

eCFR — 49 CFR Part 71: Standard Time Zone Boundaries U.S. DOT — Uniform Time & Time Zone Oversight NIST — Daylight Saving Time Rules & Arizona Exception IANA — Time Zone Database Timezone Boundary Builder — Approximate IANA Zone Geometry Natural Earth — Base Geography

Reviewed August 23, 2026. U.S. legal boundary descriptions are authoritative reference text; interactive polygons are visual aids and should not be used as legal survey boundaries.

Mountain Time Zone Map FAQ

Where is the Mountain Time Zone in the United States?

49 CFR § 71.8 defines Mountain Time as the U.S. area west of the Central–Mountain boundary in § 71.7 and east of the Mountain–Pacific boundary in § 71.9.

Which states are split between Central and Mountain Time?

The Central–Mountain line affects North Dakota, South Dakota, Nebraska, Kansas and Texas. Far-west Texas around El Paso and Hudspeth County is on Mountain Time while most of Texas is Central.

Which states are split between Mountain and Pacific Time?

Idaho and Oregon contain important Mountain–Pacific splits. The legal line also detours around West Wendover, Nevada, placing that city on the Mountain side while most of Nevada uses Pacific Time.

Does Arizona observe daylight saving time?

Most of Arizona does not observe daylight saving time and remains on MST at UTC−07:00 year-round. The Navajo Indian Reservation is an exception and does observe DST.

Why is Phoenix sometimes an hour behind Denver?

During daylight saving time Denver advances to MDT at UTC−06:00, while Phoenix remains on MST at UTC−07:00. In winter both normally show MST at UTC−07:00.

Is MST the same as Pacific Daylight Time?

No. MST and PDT can share the same UTC−07:00 offset, but they are different civil time designations with different zone identities and seasonal rules.

What time zone is Murdo, South Dakota?

49 CFR § 71.7 specifically states that Murdo is in the Central Standard Time Zone, even though municipalities directly on that boundary are otherwise assigned to Mountain Standard Time.

Why is West Wendover, Nevada important on the map?

The federal Mountain–Pacific boundary in 49 CFR § 71.9 explicitly detours around the city limits of West Wendover before returning to the Utah–Nevada boundary.

Can I print or download this map?

Yes. Use Print Map, Download SVG or Download PNG. The export reflects the current map view, selected date and visible city layer.

Is this an official legal boundary survey?

No. CalendarHours uses official legal descriptions as a reference and IANA-aligned approximate geometry for interactive visualization. For legal boundary questions, consult the current federal regulation and U.S. Department of Transportation.