AST/ADT
Atlantic Standard Time
GMT -4
12am
3am
6am
9am
12pm
3pm
6pm
9pm
ADT automatically adjusted to AST time zone, that is in use
CST/CDT
Cuba Standard Time
GMT -5
12am
3am
6am
9am
12pm
3pm
6pm
9pm
CDT automatically adjusted to CST time zone, that is in use

Time Difference

Atlantic Standard Time is 1 hour ahead of Cuba Standard Time
8:00 am08:00 in AST is 7:00 am07:00 in CST

AST to CST call time
Best time for a conference call or a meeting is between 10am-5pm in AST which corresponds to 9am-4pm in CST

8:00 am08:00 Atlantic Standard Time (AST). Offset UTC -4:00 hours
7:00 am07:00 Cuba Standard Time (CST). Offset UTC -5:00 hours

8:00 am08:00 AST / 7:00 am07:00 CST

ASTCST
12am (midnight)11pm
1am12am (midnight)
2am1am
3am2am
4am3am
5am4am
6am5am
7am6am
8am7am
9am8am
10am9am
11am10am
12pm (noon)11am
1pm12pm (noon)
2pm1pm
3pm2pm
4pm3pm
5pm4pm
6pm5pm
7pm6pm
8pm7pm
9pm8pm
10pm9pm
11pm10pm
00:0023:00
01:0000:00
02:0001:00
03:0002:00
04:0003:00
05:0004:00
06:0005:00
07:0006:00
08:0007:00
09:0008:00
10:0009:00
11:0010:00
12:0011:00
13:0012:00
14:0013:00
15:0014:00
16:0015:00
17:0016:00
18:0017:00
19:0018:00
20:0019:00
21:0020:00
22:0021:00
23:0022:00

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 time zone, however during winter some places adjust time for one hour back and observe Atlantic Standard Time (AST).

Daylight saving time clock moves forward for one hour from 2am to 3amEnd: Atlantic Daylight Time (ADT) has ended on Sunday, November 2, 2025 at 2:00 am local time and clocks were 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

Daylight saving time clock moves back for one hour from 2am to 1amStart: Atlantic Daylight Time (ADT) starts on Sunday, March 8, 2026 at 2:00 am local time and clocks are set one hour forward to Sunday, March 8, 2026, 3:00 am. Daylight saving starts annually the on second Sunday of March

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
  • 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

Cuba Daylight Time

Offset: CDT is 4 hours behind Greenwich Mean Time (GMT) and is used in Caribbean

Countries: It is used in following countries: Cuba

Principal Cities: The largest city in the CDT timezone is Havana from Cuba with population about 2.164 million people. Other major cities in the area are Santiago de Cuba, Camaguey, Holguin, Guantanamo

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

Daylight saving time clock moves forward for one hour from 1am to 2amEnd: Cuba Daylight Time (CDT) has ended on Sunday, November 2, 2025 at 1:00 am local time and clocks were set one hour back to Sunday, November 2, 2025, 12:00 am local standard time instead. Daylight saving ends annually the on first Sunday of November

Daylight saving time clock moves back for one hour from 12am to 11pmStart: Cuba Daylight Time (CDT) starts on Sunday, March 8, 2026 at 12:00 am local time and clocks are set one hour forward to Sunday, March 8, 2026, 1:00 am. Daylight saving starts annually the on second Sunday of March

CDT 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 CDT
  • Q - short form of 'Quebec'
IANA/Olson: Reflects CDT time zone boundaries defined by political bodies, primarily intended for use with computer programs and operating systems
  • America/Havana
  • Cuba
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 -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
  • HLV - Hora Legal de Venezuela
  • PYT - Paraguay Time
  • Q - Quebec Time Zone
  • VET - Venezuelan Standard Time