What is the time difference between ACST and HST?

Hawaii Standard Time (HST) is 20 hours and 30 minutes behind Australian Central Standard Time (ACST). ACST uses a UTC offset of UTC+10:30, while HST uses UTC-10. For example, when it's 9:00 AM in ACST, it's 12:30 PM in HST. Note that this difference may shift by one hour during daylight saving time transitions if ACST observes DST. Use the conversion table above to see the exact time for each hour of the day.

How do I convert ACST to HST?

To convert ACST to HST, subtract 20 hours and 30 minutes from the ACST time. For example, 9:00 AM ACST is 12:30 PM HST, and 5:00 PM ACST is 8:30 PM HST. Keep in mind that during daylight saving time transitions, the offset between these timezones may temporarily change by one hour. You can also use the interactive converter above for quick, accurate results.

What time is it in HST when it's noon in ACST?

When it's 12:00 PM (noon) in ACST, it's 3:30 PM in HST. This is because HST is 20 hours and 30 minutes behind ACST. Similarly, when it's 6:00 PM in ACST, it's 9:30 PM in HST. During daylight saving time transitions, these times may shift by one hour, so always verify the current offset. The color-coded conversion table above shows every hour mapped between both timezones.

How many hours behind is HST from ACST?

HST is 20 hours and 30 minutes behind ACST. This means when it's 9:00 AM in ACST, it's 12:30 PM in HST, and when it's midnight in ACST, it's 3:30 AM in HST. The exact difference can vary by one hour during daylight saving time transitions. The conversion table above provides a complete hour-by-hour mapping.

Is HST ahead or behind ACST?

HST is behind ACST by 20 hours and 30 minutes. Clocks in HST show an earlier time than ACST, meaning the day starts later in HST relative to ACST. For example, when it's noon in ACST, it's still 3:30 PM in HST. This gap may change by one hour during DST transitions.

Does ACST observe daylight saving time?

Yes, Australian Central Standard Time observes daylight saving time. During DST, the abbreviation changes to ACDT and clocks move forward by one hour, typically in spring. Clocks then fall back in autumn, returning to standard ACST time. This means the UTC offset for ACST shifts between two values depending on the season. Check our DST change calendar for exact transition dates that may affect your ACST to HST conversions.

Does HST observe daylight saving time?

No, Hawaii Standard Time does not observe daylight saving time. The UTC offset of UTC-10 remains the same year-round, making time conversions to HST more predictable. Countries and regions in this timezone keep their clocks unchanged regardless of the season.

What is the best time to call from ACST to HST?

The best time for a call between ACST and HST is during overlapping business hours (9 AM – 5 PM) in both timezones. To reach someone in HST during their work day, call between 5:30 AM and 1:30 PM your ACST time. Avoid calling too early or late, as the 20 hours and 30 minutes difference means your evening could be their early morning. Check the color-coded conversion table above — green hours indicate business hours in both zones, making it easy to find the ideal time.

When does daylight saving time change in ACST?

Daylight saving time transitions vary by year and region. Australian Central Standard Time observes DST, which typically shifts clocks forward by one hour in spring ("spring forward") and back in fall ("fall back"). During these transition periods, the time difference between ACST and HST may temporarily change by one hour, which can cause confusion for scheduled meetings or calls. It's important to double-check your conversions around transition dates, especially if the two timezones switch on different dates. Check our DST change calendar for exact transition dates in the current year.

Do ACST and HST ever have the same time?

No, ACST and HST never show the same time because their base UTC offsets are different. However, because ACST observes daylight saving time and HST does not, the time difference between them changes by one hour during DST transitions. This means the gap narrows or widens depending on the season, but the two clocks never align. Always verify the current offset around DST transition dates to avoid scheduling errors.

ACST to HST Converter

Convert Australian Central Standard Time to Hawaii Standard Time. See the hour-by-hour conversion table below.

Timezone Details

Australian Central Standard Time

5:13 PM

Monday, October 19, 2026

ACDT (UTC+10:30)

Hawaii Standard Time

8:43 PM

Sunday, October 18, 2026

HST (UTC-10:00)

Difference: -20h 30m

ACDT DST: Yes (ACDT)

HST DST: No

24-Hour Overview

ACDT — 24-hour overview

12a12a

3a3a

6a6a

9a9a

10a

11a

12p12p

3p3p

6p6p

9p9p

10p

11p

NightMorningBusinessEvening

HST — 24-hour overview

3a3a

6a6a

9a9a

10a

11a

12p12p

3p3p

6p6p

9p9p

10p

11p

12a12a

NightMorningBusinessEvening

Frequently Asked Questions

Related Conversions

HST to ACST

Cities in These Timezones

ACST Cities

Adelaide

HST Cities

Honolulu

More Tools

Compare ACST & HST Plan a Meeting (ACST & HST)See on Map

Learn More

How Time Zones Work Understanding DST Timezone Abbreviations

External Resources

Australian Central Standard Time on Wikipedia Hawaii Standard Time on Wikipedia IANA Time Zone Database