AST
Atlantic Standard Time
GMT -4
CST/CDT
Central Standard Time
GMT -6
CDT automatically adjusted to CST time zone, that is in use

Time Difference

Atlantic Standard Time is 2 hours ahead of Central Standard Time
So 11:00 am11:00 in AST is 9:00 am09:00 in CST

11:00 am11:00 Atlantic Standard Time (AST). Offset UTC -4:00 hours
9:00 am09:00 Central Standard Time (CST). Offset UTC -6:00 hours

11:00 am11:00 AST / 9:00 am09:00 CST

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

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 switch clocks for one hour forward when daylight saving comes into effect and observe Atlantic Daylight Time (ADT).

Start: AST starts annually on the same date and time. and clocks were set one hour back on Sunday, November 3, 2019, at 2:00 (2:00 am) local time.

End: AST ends annually on the same date and time. and clocks are set one hour forward on Sunday, March 8, 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
  • -04 -


Central Daylight Time

Offset: CDT is 5 hours behind Greenwich Mean Time (GMT) and is used in North America

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

Principal Cities: The largest city in the CDT timezone is Mexico City from Mexico with population about 12.294 million people. Other major cities in the area are Chicago, Havana, Houston, Iztapalapa

Daylight Saving: Central Daylight Time (CDT) is a daylight saving/summer timezone, however during winter some places adjust time for one hour back and observe Central Standard Time (CST).

End: CDT ends annually on the same date and time. and clocks were set one hour back on Sunday, November 3, 2019, at 2:00 (2:00 am) local time.

Start: CDT starts annually on the same date and time. and clocks are set one hour forward on Sunday, March 8, 2020, at 2:00 (2:00 am) local time.

French: HAC - Heure Avancée du Centre

Spanish: CT - Zona Centro

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

W3C/ISO-8601: International standard covering representation and exchange of dates and time-related data
  • -05 - basic short
  • -0500 - basic
  • -05:00 - extended

Email/RFC-2822: Internet Message Format Date Standard, typically used for timestamps in email headers
  • -0500 - sign character (-) followed by a four digit time providing hours (05) and minutes (00) of the offset. Indicates five 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
  • Romeo - Military abbreviation for CDT
  • R - short form of 'Romeo'

IANA/Olson: Reflects CDT time zone boundaries defined by political bodies, primarily intended for use with computer programs and operating systems
  • America/Bahia_Banderas
  • America/Chicago
  • America/Indiana/Knox
  • America/Indiana/Tell_City
  • America/Knox_IN
  • America/Matamoros
  • America/Menominee
  • America/Merida
  • America/Mexico_City
  • America/Monterrey
  • America/North_Dakota/Beulah
  • America/North_Dakota/Center
  • America/North_Dakota/New_Salem
  • America/Rainy_River
  • America/Rankin_Inlet
  • America/Resolute
  • America/Winnipeg
  • CST6CDT
  • Canada/Central
  • Mexico/General
  • US/Central
  • US/Indiana-Starke

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

  • Central Daylight Time - UTC -5
  • Cuba Daylight Time - UTC -4

Time zones with the GMT -5 offset:

  • CDT - Central Daylight Time
  • EST - Eastern Standard Time
  • ET - Eastern Time
  • COT - Colombia Time
  • CST - Cuba Standard Time
  • EASST - Easter Island Summer Time
  • ECT - Ecuador Time
  • PET - Peru Time
  • R - Romeo Time Zone
  • -05 -