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HAST to HDT Converter

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HAST
Hawaii-Aleutian Standard Time
GMT -10
12am
3am
6am
9am
12pm
3pm
6pm
9pm
HAST is not used on this date
This converter keeps HAST at GMT -10. Adak uses HDT (GMT -9) on this date. Open the HDT converter.
HDT
Hawaii Daylight Time
GMT -9
12am
3am
6am
9am
12pm
3pm
6pm
9pm
HDT is not used on this date
This converter keeps HDT at GMT -9. Honolulu uses HST (GMT -10) on this date. Open the HST converter, or choose Honolulu, Pearl City, or Hilo for city-specific time.

Quick answers

Selected conversion

2:00 am02:00 HAST (UTC-10), Oct 12, 2026 = 3:00 am03:00 HDT (UTC-9), Oct 12, 2026

HAST is 1 hour behind HDT.

HAST and HDT examples

These examples always use HAST (UTC-10) 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.

HAST is 1 hour behind HDT.

How the time difference changes

HAST is 1 hour behind HDT year-round.

Working hours of 9:00 am to 5:00 pm in HAST correspond to 10:00 am to 6:00 pm in HDT.Working hours of 09:00 to 17:00 in HAST correspond to 10:00 to 18:00 in HDT.

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

Time Difference

Hawaii-Aleutian Standard Time is 1 hour behind Hawaii Daylight Time.
2:00 am02:00 in HAST is 3:00 am03:00 in HDT

HAST to HDT call time
Best time for a conference call or a meeting is between 9am-4pm09:00-16:00 in HAST which corresponds to 10am-5pm10:00-17:00 in HDT

2:00 am02:00 Hawaii-Aleutian Standard Time (HAST). Offset UTC -10:00 hours
3:00 am03:00 Hawaii Daylight Time (HDT). Offset UTC -9:00 hours

2:00 am02:00 HAST / 3:00 am03:00 HDT

HASTHDT
12:00am1:00am
1:00am2:00am
2:00am3:00am
3:00am4:00am
4:00am5:00am
5:00am6:00am
6:00am7:00am
7:00am8:00am
8:00am9:00am
9:00am10:00am
10:00am11:00am
11:00am12:00pm
12:00pm1:00pm
1:00pm2:00pm
2:00pm3:00pm
3:00pm4:00pm
4:00pm5:00pm
5:00pm6:00pm
6:00pm7:00pm
7:00pm8:00pm
8:00pm9:00pm
9:00pm10:00pm
10:00pm11:00pm
11:00pm12:00am
00:0001:00
01:0002:00
02:0003:00
03:0004:00
04:0005:00
05:0006:00
06:0007:00
07:0008:00
08:0009:00
09:0010:00
10:0011:00
11:0012:00
12:0013:00
13:0014:00
14:0015:00
15:0016:00
16:0017:00
17:0018:00
18:0019:00
19:0020:00
20:0021:00
21:0022:00
22:0023:00
23:0000:00

Hawaii-Aleutian Standard Time

Offset: HAST is 10 hours behind Greenwich Mean Time (GMT) and is used in America

Daylight Saving: This is a standard time zone. During summer, some places set clocks forward one hour for daylight saving time and observe Hawaii-Aleutian Daylight Time (HADT).

Daylight saving time clock moves forward for one hourEnd: Hawaii-Aleutian Standard Time (HAST) ended on Sunday, March 8, 2026 at 2:00 am02:00 local time and clocks were set one hour forward to Sunday, March 8, 2026, 3:00 am03:00 local daylight time instead. Standard time ends annually on the second Sunday of March.

Daylight saving time clock moves back for one hourStart: Hawaii-Aleutian Standard Time (HAST) starts on Sunday, November 1, 2026 at 2:00 am02:00 local time and clocks are set one hour back to Sunday, November 1, 2026, 1:00 am01:00. Standard time starts annually on the first Sunday of November.

See upcoming clock changes worldwide.

HAST representations, usage and related time zones

W3C/ISO-8601: International standard covering representation and exchange of dates and time-related data
  • -10 - basic short
  • -1000 - basic
  • -10:00 - extended
Email/RFC-2822: Internet Message Format Date Standard, typically used for timestamps in email headers
  • -1000 - sign character (-) followed by a four digit time providing hours (10) and minutes (00) of the offset. Indicates an offset of ten hours to the west of the zero meridian.
Military/NATO: Used by the U.S. military, Chinese military and others
  • Whiskey - Military abbreviation for HAST
  • W - short form of 'Whiskey'
Time zones with the GMT -10 offset:
  • HAST - Hawaii-Aleutian Standard Time
  • CKT - Cook Island Time
  • HST - Hawaii Standard Time
  • TAHT - Tahiti Time
  • W - Whiskey Time Zone

Hawaii Daylight Time

Offset: HDT is 9 hours behind Greenwich Mean Time (GMT) and is used in Pacific

Countries using this time zone: United States

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 Daylight Time
  • V - Victor Time Zone
EST to ISTGMT to ESTPST to ESTEST to GMTPST to GMT