UTC
Universal Time Coordinated
GMT +0
ADT/AST
Atlantic Daylight Time
GMT -3
AST automatically adjusted to ADT time zone, that is in use

Time Difference

Universal Time Coordinated is 3 hours ahead of Atlantic Daylight Time
So 12:00 pm12:00 in UTC is 9:00 am09:00 in ADT

12:00 pm12:00 Universal Time Coordinated (UTC). Offset UTC 0:00 hours
9:00 am09:00 Atlantic Daylight Time (ADT). Offset UTC -3:00 hours

12:00 pm12:00 UTC / 9:00 am09:00 ADT

UTC ADT
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

Universal Time Coordinated

Offset: UTC is 0 hours ahead Greenwich Mean Time (GMT) and is used in Universal

Coordinated Universal Time (UTC) is the world time standard that regulates clocks and time. It is successor to Greenwich Mean Time (GMT). For casual use, UTC is the same as GMT, but is used by the scientific community.
UTC is the time standard commonly used across the world since 1972. It is used in many technical fields, like aviation industry and meteorologists, also used to synchronize time across internet networks.

UTC representations, usage and related time zones

W3C/ISO-8601: International standard covering representation and exchange of dates and time-related data
  • Z - is the zone designator for the zero UTC/GMT offset, also known as 'Zulu' time
  • +00 - basic short
  • +0000 - basic
  • +00:00 - extended

Email/RFC-2822: Internet Message Format Date Standard, typically used for timestamps in email headers
  • +0000 - sign character (+) followed by a four digit time providing hours (00) and minutes (00) of the offset. Indicates zero hour and zero minutes time differences of the zero meridian.

Military/NATO: Used by the U.S. military, Chinese military and others
  • Zulu - Military abbreviation for UTC
  • Z - short form of 'Zulu'

IANA/Olson: Reflects UTC time zone boundaries defined by political bodies, primarily intended for use with computer programs and operating systems
  • Etc/UCT
  • Etc/UTC
  • Etc/Universal
  • Etc/Zulu
  • UCT
  • UTC
  • Universal
  • Zulu

Time zones with the GMT +0 offset:

  • EGST - Eastern Greenland Summer Time
  • GMT - Greenwich Mean Time
  • WET - Western European Time
  • AZOST - Azores Summer Time
  • UTC - Universal Time Coordinated
  • WT - Western Sahara Standard Time
  • Z - Zulu Time Zone
  • GMT - GMT


Atlantic Standard Time

Offset: AST is 4 hours behind Greenwich Mean Time (GMT) and is used in North America

Countries: It is used in following countries: Antigua & Barbuda, Anguilla, Aruba, Barbados, St Barthelemy, Bermuda, Caribbean NL, Canada, Curaçao, Dominica, Dominican Republic, Grenada, Greenland, Guadeloupe, St Kitts & Nevis, St Lucia, St Martin (French), Martinique, Montserrat, Puerto Rico, St Maarten (Dutch), Trinidad & Tobago, St Vincent, Virgin Islands (UK), Virgin Islands (US)

Principal Cities: The largest city in the AST timezone is Santo Domingo from Dominican Republic with population about 2.202 million people. Other major cities in the area are Santiago de los Caballeros, Santo Domingo Oeste, San Juan, Halifax

Daylight Saving: This is a standard timezone, however during summer some places adjust time for one hour forward for daylight saving and observe Atlantic Daylight Time (ADT).

End: AST ended and clocks were set one hour forward on Sunday, 08 March 2020, at 2:00 (2:00 am) local time.

Start: AST starts and clocks are set one hour back on Sunday, 01 November 2020, at 2:00 (2:00 am) local time.

French: HNA - Heure Normale de l'Atlantique

Spanish: AST - Tiempo Estándar del Atlántico

AST Time Zone Geo Map
AST timezone map
AST representations, usage and related time zones

W3C/ISO-8601: International standard covering representation and exchange of dates and time-related data
  • -04 - basic short
  • -0400 - basic
  • -04:00 - extended

Email/RFC-2822: Internet Message Format Date Standard, typically used for timestamps in email headers
  • -0400 - sign character (-) followed by a four digit time providing hours (04) and minutes (00) of the offset. Indicates four 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
  • Quebec - Military abbreviation for AST
  • Q - short form of 'Quebec'

IANA/Olson: Reflects AST time zone boundaries defined by political bodies, primarily intended for use with computer programs and operating systems
  • America/Anguilla
  • America/Antigua
  • America/Aruba
  • America/Barbados
  • America/Blanc-Sablon
  • America/Curacao
  • America/Dominica
  • America/Glace_Bay
  • America/Goose_Bay
  • America/Grenada
  • America/Guadeloupe
  • America/Halifax
  • America/Kralendijk
  • America/Lower_Princes
  • America/Marigot
  • America/Martinique
  • America/Moncton
  • America/Montserrat
  • America/Port_of_Spain
  • America/Puerto_Rico
  • America/Santo_Domingo
  • America/St_Barthelemy
  • America/St_Kitts
  • America/St_Lucia
  • America/St_Thomas
  • America/St_Vincent
  • America/Thule
  • America/Tortola
  • America/Virgin
  • Atlantic/Bermuda
  • Canada/Atlantic

AST Abbreviation: Several time zones share AST abbreviation and it could refer to these time zones

  • Atlantic Standard Time - UTC -4
  • Arabia Standard Time - UTC +3

Time zones with the GMT -4 offset:

  • AST - Atlantic Standard Time
  • EDT - Eastern Daylight Time
  • AMT - Amazon Time
  • BOT - Bolivia Time
  • CDT - Cuba Daylight Time
  • CLT - Chile Standard Time
  • FKT - Falkland Island Time
  • GYT - Guyana Time
  • PYT - Paraguay Time
  • Q - Quebec Time Zone
  • VET - Venezuelan Standard Time
  • GMT - GMT-04:00
  • -04 -