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This converter keeps HDT at UTC−9. Adak uses HST (UTC−10) on this date. Open the HST converter, or choose Honolulu, Pearl City, or Hilo for city-specific time.

Quick answers

Selected conversion

5:30 pm17:30 GMT (UTC+0), Nov 1, 2026 = 8:30 am08:30 HDT (UTC-9), Nov 1, 2026

GMT is 9 hours ahead of HDT.

GMT and HDT examples

These examples always use GMT (UTC+0) and HDT (UTC-9). They stay the same when you change the date or time above. The selected conversion may differ when daylight saving time applies.

GMT is 9 hours ahead of HDT.

How the time difference changes

GMT is 9 hours ahead of HDT year-round.

Working hours of 9:00 am to 6:00 pm in GMT correspond to 12:00 am to 9:00 am in HDT.Working hours of 09:00 to 18:00 in GMT correspond to 00:00 to 09:00 in HDT.

Compare GMT time with HDT time, including current local time, UTC offsets, time difference, daylight saving changes, working hours, and shareable meeting times.

Time Difference

Greenwich Mean Time is 9 hours ahead of Hawaii-Aleutian Daylight Time.
5:30 pm17:30 in GMT is 8:30 am08:30 in HDT

GMT to HDT call time
Best time for a conference call or a meeting is between 5:30pm-6:30pm17:30-18:30 in GMT which corresponds to 8:30am-9:30am08:30-09:30 in HDT. Their 9am–6pm09:00–18:00 working hours do not overlap; this is a suggested compromise.

5:30 pm17:30 Greenwich Mean Time (GMT). Offset UTC 0:00 hours
8:30 am08:30 Hawaii-Aleutian Daylight Time (HDT). Offset UTC -9:00 hours

5:30 pm17:30 GMT / 8:30 am08:30 HDT

Choose an hour to update the converter. Day labels such as “next day” or “+1” are relative to the selected date in the first column. Use Up and Down arrow keys, Home or End to move between hours, then Enter or Space to select.

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Greenwich Mean Time

Offset: GMT is the same as Greenwich Mean Time (GMT).

Countries using this time zone: Antarctica, Burkina Faso, Gambia, Ghana, Greenland, Guernsey, Guinea, Guinea-Bissau, Iceland, Ireland, Isle of Man, Ivory Coast, Jersey, Liberia, Mali, Mauritania, Morocco, Saint Helena, São Tomé and Príncipe, Senegal, Sierra Leone, Togo, United Kingdom, Western Sahara

Principal Cities: The largest city in the GMT time zone is London in the United Kingdom, with about 8.962 million people. Other major cities in this time zone include Abidjan, Bamako, Casablanca, Dakar.

Greenwich Mean Time (GMT) originally referred to the mean solar time at the Royal Observatory in Greenwich, London. It is now often used to refer to Coordinated Universal Time (UTC) when this is viewed as a time zone, and in casual use the two are the same. In the military, GMT is known as Zulu time. Greenwich Mean Time was the same as Universal Time (UT), a standard astronomical concept used in many technical fields, until the introduction of UTC in 1972.

Map of the areas on Greenwich Mean Time (GMT)
GMT all year GMT part of the year

Today all shaded areas are on GMT.

GMT 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 the zero UTC/GMT offset.
Military/NATO: Used by the U.S. military, Chinese military and others
  • Zulu - Military abbreviation for GMT
  • Z - short form of 'Zulu'
IANA/Olson: Reflects GMT time zone boundaries defined by political bodies, primarily intended for use with computer programs and operating systems
  • Africa/Abidjan
  • Africa/Accra
  • Africa/Bamako
  • Africa/Banjul
  • Africa/Bissau
  • Africa/Conakry
  • Africa/Dakar
  • Africa/Freetown
  • Africa/Lome
  • Africa/Monrovia
  • Africa/Nouakchott
  • Africa/Ouagadougou
  • Africa/Sao_Tome
  • Africa/Timbuktu
  • America/Danmarkshavn
  • Atlantic/Reykjavik
  • Atlantic/St_Helena
  • Eire
  • Etc/GMT
  • Etc/GMT+0
  • Etc/GMT-0
  • Etc/GMT0
  • Etc/Greenwich
  • Europe/Belfast
  • Europe/Dublin
  • Europe/Guernsey
  • Europe/Isle_of_Man
  • Europe/Jersey
  • Europe/London
  • GB
  • GB-Eire
  • GMT
  • GMT+0
  • GMT-0
  • GMT0
  • Greenwich
  • Iceland
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 - Coordinated Universal Time
  • WT - Western Sahara Standard Time
  • Z - Zulu Time Zone

Hawaii-Aleutian Daylight Time

Offset: HDT is 9 hours behind Greenwich Mean Time (GMT).

Countries using this time zone: United States

Map of the areas on Hawaii-Aleutian Daylight Time (HDT)
HDT part of the year

Today the shaded areas are on UTC−10 (HST).

Daylight Saving: Hawaii-Aleutian Daylight Time (HDT) is a daylight saving/summer time zone, but some places set clocks back one hour during winter and observe Hawaii-Aleutian Standard Time (HAST).

123456789101112End: Hawaii-Aleutian Daylight Time (HDT) ended on Sunday, November 1, 2026 at 2:00 am02:00 local time and clocks were set one hour back to Sunday, November 1, 2026, 1:00 am01:00 local standard time instead. Daylight saving ends annually on the first Sunday of November.

123456789101112Start: Hawaii-Aleutian Daylight Time (HDT) starts on Sunday, March 14, 2027 at 2:00 am02:00 local time and clocks are set one hour forward to Sunday, March 14, 2027, 3:00 am03:00. Daylight saving starts annually on the second Sunday of March.

See USA daylight saving time and upcoming clock changes worldwide.

HDT representations, usage and related time zones

W3C/ISO-8601: International standard covering representation and exchange of dates and time-related data
  • -09 - basic short
  • -0900 - basic
  • -09:00 - extended
Email/RFC-2822: Internet Message Format Date Standard, typically used for timestamps in email headers
  • -0900 - sign character (-) followed by a four digit time providing hours (09) and minutes (00) of the offset. Indicates an offset of nine hours to the west of the zero meridian.
Military/NATO: Used by the U.S. military, Chinese military and others
  • Victor - Military abbreviation for HDT
  • V - short form of 'Victor'
IANA/Olson: Reflects HDT time zone boundaries defined by political bodies, primarily intended for use with computer programs and operating systems
  • America/Adak
  • America/Atka
  • US/Aleutian
Time zones with the GMT -9 offset:
  • AKST - Alaska Standard Time
  • AHDT - Alaska-Hawaii Daylight Time
  • HADT - Hawaii-Aleutian Daylight Time
  • GAMT - Gambier Time
  • HDT - Hawaii-Aleutian Daylight Time
  • V - Victor Time Zone