The
Mountain Time Zone
of
North America
keeps time by subtracting seven hours from
Coordinated Universal Time
(UTC) when
standard time
(
UTC?07:00
) is in effect, and by subtracting six hours during
daylight saving time
(
UTC?06:00
). The clock time in this zone is based on the
mean solar time
at the
105th meridian west
of the
Greenwich Observatory
. In the United States, the exact specification for the location of
time zones
and the dividing lines between zones is set forth in the
Code of Federal Regulations
at 49 CFR 71.
[a]
In the United States and Canada, this time zone is generically called
Mountain Time
(
MT
). Specifically, it is
Mountain Standard Time
(
MST
) when observing standard time, and
Mountain Daylight Time
(
MDT
) when observing daylight saving time. The term refers to the
Rocky Mountains
, which range from
British Columbia
to
New Mexico
. In Mexico, this time zone is known as the
tiempo de la montana
or
zona Pacifico
("Pacific Zone"). In the United States and Canada, the Mountain Time Zone is to the east of the
Pacific Time Zone
and to the west of the
Central Time Zone
.
In some areas, starting in 2007, the local time changes from MST to MDT at 2
am MST to 3
am MDT on the second Sunday in March and returns at 2
am MDT to 1
am MST on the first Sunday in November.
Sonora
in Mexico and most of
Arizona
in the United States do not observe daylight saving time (DST), and during the spring, summer, and autumn months they are on the same time as
Pacific Daylight Time
.
[4]
The
Navajo Nation
, most of which lies within Arizona but extends into Utah and New Mexico (which do observe DST), does observe DST, although the
Hopi Reservation
, as well as some Arizona state offices lying within the Navajo Nation, do not.
The largest city in the Mountain Time Zone is
Phoenix, Arizona
; the
Phoenix metropolitan area
is the largest metropolitan area in the zone.
One province and two territories are fully contained in the Mountain Time Zone:
On September 24, 2020, Yukon switched to the Mountain Standard Time year-round. Therefore, clocks in Yukon and Alberta are the same in the winter, and Alberta is one hour ahead in summer. Previously, the territory had used the Pacific Time Zone with daylight saving time: UTC?8 in winter and UTC?7 in summer.
[5]
One province and one territory are split between the Mountain Time Zone and the
Pacific Time Zone
:
One territory and one province are split between the Mountain Time Zone and the
Central Time Zone
:
The following
states
have the same time as Mountain Time Zone:
Six states are fully contained in the Mountain Time Zone:
Three states are split between the Mountain Time Zone and the
Pacific Time Zone
. The following locations observe Mountain Time:
Five states are split between the Mountain Time Zone and the
Central Time Zone
. The following locations observe Mountain Time:
- Kansas
:
Sherman
,
Wallace
,
Greeley
and
Hamilton
Counties
- Nebraska
: western one third
- North Dakota
: the southwest corner counties (
Adams
,
Billings
,
Bowman
,
Golden Valley
,
Grant
,
Hettinger
,
Slope
,
Stark
) observe MST. The counties of
McKenzie
,
Dunn
, and
Sioux
are split.
- South Dakota
: western half
- Texas
:
El Paso
,
Hudspeth
, and northwestern
Culberson
Counties
Major metropolitan areas
edit
Alphabetical list of major cities located within the Mountain Time Zone. Cities in
bold
do not observe daylight saving time:
- Albuquerque, New Mexico
- Billings, Montana
- Boise, Idaho
- Boulder, Colorado
- Calgary
,
Alberta
- Cheyenne, Wyoming
- Chihuahua, Chihuahua
- Ciudad Juarez
,
Chihuahua
- Ciudad Obregon
,
Sonora
- Colorado Springs, Colorado
- Culiacan
,
Sinaloa
- Metropolitan Denver
- Edmonton
,
Alberta
- El Paso, Texas
- Flagstaff, Arizona
- Fort Collins, Colorado
- Greeley, Colorado
- Hermosillo
,
Sonora
- La Paz, Baja California Sur
- Lake Havasu City, Arizona
- Lethbridge
,
Alberta
- Los Mochis
,
Sinaloa
- Mazatlan
,
Sinaloa
- Missoula, Montana
- Nogales, Sonora
- Metropolitan Phoenix
- Provo, Utah
- Pueblo, Colorado
- Rapid City, South Dakota
- Red Deer, Alberta
- Salt Lake City
,
Utah
- San Luis Rio Colorado
,
Sonora
- Tepic
,
Nayarit
- Tucson, Arizona
- West Jordan, Utah
- West Valley City, Utah
- Yuma, Arizona
- ^
The specification for the Mountain Time Zone in the United States is set forth at 49 CFR 71.8.
[1]
The boundary between Central and Mountain time zones is set forth at 49 CFR 71.7,
[2]
and the boundary between Mountain and Pacific time zones is set forth at 49 CFR 71.9.
[3]