ADT
Atlantic Daylight Time
GMT -3
MDT/MST
Mountain Daylight Time
GMT -6
MST automatically adjusted to MDT time zone, that is in use

Time Difference

Atlantic Daylight Time is 3 hours ahead of Mountain Daylight Time
10:30 am10:30 in ADT is 7:30 am07:30 in MDT

ADT to MST call time
Best time for a conference call or a meeting is between 12pm-6pm in ADT which corresponds to 8am-2pm in MST

10:30 am10:30 Atlantic Daylight Time (ADT). Offset UTC -3:00 hours
7:30 am07:30 Mountain Daylight Time (MDT). Offset UTC -6:00 hours

10:30 am10:30 ADT / 7:30 am07:30 MDT

ADT MDT
12am (midnight) 9pm
1am 10pm
2am 11pm
3am 12am (midnight)
4am 1am
5am 2am
6am 3am
7am 4am
8am 5am
9am 6am
10am 7am
11am 8am
12pm (noon) 9am
1pm 10am
2pm 11am
3pm 12pm (noon)
4pm 1pm
5pm 2pm
6pm 3pm
7pm 4pm
8pm 5pm
9pm 6pm
10pm 7pm
11pm 8pm
0:00 21:00
1:00 22:00
2:00 23:00
3:00 0:00
4:00 1:00
5:00 2:00
6:00 3:00
7:00 4:00
8:00 5:00
9:00 6:00
10:00 7:00
11:00 8:00
12:00 9:00
13:00 10:00
14:00 11:00
15:00 12:00
16:00 13:00
17:00 14:00
18:00 15:00
19:00 16:00
20:00 17:00
21:00 18:00
22:00 19:00
23:00 20:00

Atlantic Daylight Time

Offset: ADT is 3 hours behind Greenwich Mean Time (GMT) and is used in North America

Countries: It is used in following countries: Bermuda, Canada, Greenland

Principal Cities: The largest city in the ADT timezone is Halifax from Canada with population about 359,111 people. Other major cities in the area are Sydney, Dartmouth, Saint John, Moncton

French: HAA - Heure Avancée de l'Atlantique

ADT Time Zone Geo Map
ADT timezone map

Daylight Saving: Atlantic Daylight Time (ADT) is a daylight saving/summer timezone, however during winter some places switch clocks for one hour back and observe Atlantic Standard Time (AST).

Daylight saving time clock moves forward for one hour from 2am to 3amStart: Atlantic Daylight Time (ADT) started on Sunday, March 9, 2025 at 2:00 am local time and clocks were set one hour forward to Sunday, March 9, 2025, 3:00 am. Daylight saving starts annually the on second Sunday of March

Daylight saving time clock moves back for one hour from 2am to 1amEnd: Atlantic Daylight Time (ADT) ends on Sunday, November 2, 2025 at 2:00 am local time and clocks are set one hour back to Sunday, November 2, 2025, 1:00 am local standard time instead. Daylight saving ends annually the on first Sunday of November

ADT representations, usage and related time zones

W3C/ISO-8601: International standard covering representation and exchange of dates and time-related data
  • -03 - basic short
  • -0300 - basic
  • -03:00 - extended
Email/RFC-2822: Internet Message Format Date Standard, typically used for timestamps in email headers
  • -0300 - sign character (-) followed by a four digit time providing hours (03) and minutes (00) of the offset. Indicates three hour and zero minutes time differences to the west of the zero meridian.
Military/NATO: Used by the U.S. military, Chinese military and others
  • Papa - Military abbreviation for ADT
  • P - short form of 'Papa'
IANA/Olson: Reflects ADT time zone boundaries defined by political bodies, primarily intended for use with computer programs and operating systems
  • America/Glace_Bay
  • America/Goose_Bay
  • America/Halifax
  • America/Moncton
  • America/Thule
  • Atlantic/Bermuda
  • Canada/Atlantic
Time zones with the GMT -3 offset:
  • ADT - Atlantic Daylight Time
  • PMT - Pierre & Miquelon Standard Time
  • PMST - Pierre & Miquelon Standard Time
  • WGT - West Greenland Time
  • AMST - Amazon Summer Time
  • ART - Argentina Time
  • BRT - Brasília time
  • CLST - Chile Summer Time
  • FKST - Falkland Islands Summer Time
  • GFT - French Guiana Time
  • P - Papa Time Zone
  • PYST - Paraguay Summer Time
  • SRT - Suriname Time
  • UYT - Uruguay Time

Mountain Standard Time

Offset: MST is 7 hours behind Greenwich Mean Time (GMT) and is used in North America

Countries: It is used in following countries: Canada, Mexico, United States

Principal Cities: The largest city in the MST timezone is Phoenix from USA with population about 1.446 million people. Other major cities in the area are Calgary, Edmonton, El Paso, Denver

French: HNR - Heure Normale des Rocheuses

Spanish: MT - Zona Pacífico

MST Time Zone Geo Map
MST timezone map

Daylight Saving: This is a standard time zone, however during summer some places switch clocks for one hour forward when daylight saving comes into effect and observe Mountain Daylight Time (MDT).

Daylight saving time clock moves forward for one hour from 2am to 3amEnd: Mountain Standard Time (MST) has ended on Sunday, March 9, 2025 at 2:00 am local time and clocks were set one hour forward to Sunday, March 9, 2025, 3:00 am local daylight time instead. Standard time ends annually the on second Sunday of March.

Daylight saving time clock moves back for one hour from 2am to 1amStart: Mountain Standard Time (MST) starts on Sunday, November 2, 2025 at 2:00 am local time and clocks are set one hour back to Sunday, November 2, 2025, 1:00 am. Standard time starts annually the on first Sunday of November.

MST representations, usage and related time zones

W3C/ISO-8601: International standard covering representation and exchange of dates and time-related data
  • -07 - basic short
  • -0700 - basic
  • -07:00 - extended
Email/RFC-2822: Internet Message Format Date Standard, typically used for timestamps in email headers
  • -0700 - sign character (-) followed by a four digit time providing hours (07) and minutes (00) of the offset. Indicates seven hour and zero minutes time differences to the west of the zero meridian.
Military/NATO: Used by the U.S. military, Chinese military and others
  • Tango - Military abbreviation for MST
  • T - short form of 'Tango'
IANA/Olson: Reflects MST time zone boundaries defined by political bodies, primarily intended for use with computer programs and operating systems
  • America/Boise
  • America/Cambridge_Bay
  • America/Ciudad_Juarez
  • America/Creston
  • America/Dawson
  • America/Dawson_Creek
  • America/Denver
  • America/Edmonton
  • America/Fort_Nelson
  • America/Hermosillo
  • America/Inuvik
  • America/Mazatlan
  • America/Phoenix
  • America/Shiprock
  • America/Whitehorse
  • America/Yellowknife
  • Canada/Mountain
  • Canada/Yukon
  • MST
  • MST7MDT
  • Mexico/BajaSur
  • Navajo
  • US/Arizona
  • US/Mountain
MST Abbreviation: Several time zones share MST abbreviation and it could refer to these time zones
  • Mountain Standard Time - UTC -7
  • Moscow Standard Time - UTC +3
  • Mauritius Standard Time - UTC +4
Time zones with the GMT -7 offset:
  • MST - Mountain Standard Time
  • PDT - Pacific Daylight Time
  • YST - Yukon Standard Time
  • T - Tango Time Zone