ACST
Australian Central Standard Time
GMT +9:30
HST
Hawaii Standard Time
GMT -10

Time Difference

Australian Central Standard Time is 19 hours and 30 minutes ahead of Hawaii Standard Time
5:30 pm17:30 in ACST is 10:00 pm22:00 in HST

ACST to HST call time
Best time for a conference call or a meeting is between 10:30pm-12:30pm in ACST which corresponds to 3am-5am in HST

5:30 pm17:30 Australian Central Standard Time (ACST). Offset UTC +9:30 hours
10:00 pm22:00 Hawaii Standard Time (HST). Offset UTC -10:00 hours

5:30 pm17:30 ACST / 10:00 pm22:00 HST

ACST HST
12am (midnight) 4:30 am
1am 5:30 am
2am 6:30 am
3am 7:30 am
4am 8:30 am
5am 9:30 am
6am 10:30 am
7am 11:30 am
8am 12:30 pm
9am 1:30 pm
10am 2:30 pm
11am 3:30 pm
12pm (noon) 4:30 pm
1pm 5:30 pm
2pm 6:30 pm
3pm 7:30 pm
4pm 8:30 pm
5pm 9:30 pm
6pm 10:30 pm
7pm 11:30 pm
8pm 12:30 am
9pm 1:30 am
10pm 2:30 am
11pm 3:30 am
0:00 4:30
1:00 5:30
2:00 6:30
3:00 7:30
4:00 8:30
5:00 9:30
6:00 10:30
7:00 11:30
8:00 12:30
9:00 13:30
10:00 14:30
11:00 15:30
12:00 16:30
13:00 17:30
14:00 18:30
15:00 19:30
16:00 20:30
17:00 21:30
18:00 22:30
19:00 23:30
20:00 0:30
21:00 1:30
22:00 2:30
23:00 3:30

Australian Central Standard Time

Offset: ACST is 9 hours and 30 minutes ahead Greenwich Mean Time (GMT) and is used in Australia

Countries: It is used in following countries: Australia

Principal Cities: The largest city in the ACST timezone is Adelaide from Australia with population about 1.225 million people. Other major cities in the area are Darwin, Adelaide Hills, Alice Springs, Palmerston

ACST Time Zone Geo Map
ACST timezone map

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 Australian Central Daylight Time (ACDT).

Daylight saving time clock moves back for one hour from 3am to 2amStart: Australian Central Standard Time (ACST) started on Sunday, April 6, 2025 at 3:00 am local time and clocks were set one hour back to Sunday, April 6, 2025, 2:00 am. Standard time starts annually the on first Sunday of April.

Daylight saving time clock moves forward for one hour from 2am to 3amEnd: Australian Central Standard Time (ACST) ends on Sunday, October 5, 2025 at 2:00 am local time and clocks are set one hour forward to Sunday, October 5, 2025, 3:00 am local daylight time instead. Standard time starts annually the on first Sunday of October.

ACST representations, usage and related time zones

W3C/ISO-8601: International standard covering representation and exchange of dates and time-related data
  • +0930 - basic
  • +09:30 - extended
Email/RFC-2822: Internet Message Format Date Standard, typically used for timestamps in email headers
  • +0930 - sign character (+) followed by a four digit time providing hours (09) and minutes (30) of the offset. Indicates nine hour and thirty minutes time differences to the east of the zero meridian.
IANA/Olson: Reflects ACST time zone boundaries defined by political bodies, primarily intended for use with computer programs and operating systems
  • Australia/Adelaide
  • Australia/Broken_Hill
  • Australia/Darwin
  • Australia/North
  • Australia/South
  • Australia/Yancowinna

Hawaii Standard Time

Offset: HST is 10 hours behind Greenwich Mean Time (GMT) and is used in Pacific

Countries: It is used in following countries: United States

Principal Cities: The largest city in the HST timezone is Honolulu from USA with population about 371,657 people. Other major cities in the area are Pearl City, Hilo, Kailua, Waipahu

Daylight Saving: Hawaii Standard Time (HST) is not adjusted for daylight saving therefore HST remains the same through out the year. This means, unlike some time zones where the clock is set forward by one hour every summer and backward by one hour during winter to adjust for daylight saving, Hawaii Standard Time remains the same

HST Time Zone Geo Map
HST timezone map

HST 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 ten 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
  • Whiskey - Military abbreviation for HST
  • W - short form of 'Whiskey'
IANA/Olson: Reflects HST time zone boundaries defined by political bodies, primarily intended for use with computer programs and operating systems
  • America/Adak
  • America/Atka
  • HST
  • Pacific/Honolulu
  • Pacific/Johnston
  • US/Aleutian
  • US/Hawaii
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