What is the time difference between HST and ACST?

Australian Central Standard Time (ACST) is 20 hours and 30 minutes ahead of Hawaii Standard Time (HST). HST uses a UTC offset of UTC-10, while ACST uses UTC+10:30. For example, when it's 9:00 AM in HST, it's 5:30 AM in ACST. 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 HST to ACST?

To convert HST to ACST, add 20 hours and 30 minutes to the HST time. For example, 9:00 AM HST is 5:30 AM ACST, and 5:00 PM HST is 1:30 PM ACST. 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 ACST when it's noon in HST?

When it's 12:00 PM (noon) in HST, it's 8:30 AM in ACST. This is because ACST is 20 hours and 30 minutes ahead of HST. Similarly, when it's 6:00 PM in HST, it's 2:30 PM in ACST. 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 ahead is ACST from HST?

ACST is 20 hours and 30 minutes ahead of HST. This means when it's 9:00 AM in HST, it's 5:30 AM in ACST, and when it's midnight in HST, it's 8:30 PM in ACST. 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 ACST ahead or behind HST?

ACST is ahead of HST by 20 hours and 30 minutes. Clocks in ACST show a later time than HST, meaning the day starts earlier in ACST relative to HST. For example, when it's morning in HST, it's already afternoon or evening in ACST. This gap may change by one hour during DST transitions.

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 from HST more predictable. Countries and regions in this timezone keep their clocks unchanged regardless of the season.

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 HST to ACST conversions.

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

The best time for a call between HST and ACST is during overlapping business hours (9 AM – 5 PM) in both timezones. To reach someone in ACST during their work day, call between 12:30 PM and 8:30 PM your HST time. Avoid calling too early or late, as the 20 hours and 30 minutes difference means your evening could be their late night. 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 HST and ACST 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 HST and ACST ever have the same time?

No, HST and ACST 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.

HST to ACST Converter

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

Upcoming DST Change

Australian Central Time (ACDT) will fall back on April 5. Clocks will shift by 1 hour (ACDT → ACST).

View all DST changes

Timezone Details

Hawaii Standard Time

4:53 PM

Thursday, April 2, 2026

HST (UTC-10:00)

Australian Central Standard Time

1:23 PM

Friday, April 3, 2026

ACDT (UTC+10:30)

Difference: +20h 30m

HST DST: No

ACDT DST: Yes (ACDT)

24-Hour Overview

HST — 24-hour overview

12a12a

3a3a

6a6a

9a9a

10a

11a

12p12p

3p3p

6p6p

9p9p

10p

11p

NightMorningBusinessEvening

ACDT — 24-hour overview

8p8p

10p

11p11p

12a

2a2a

5a5a

8a8a

10a

11a11a

12p

2p2p

5p5p

NightMorningBusinessEvening

Frequently Asked Questions

Related Conversions

ACST to HST

Cities in These Timezones

HST Cities

Honolulu

ACST Cities

Adelaide

More Tools

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

Learn More

How Time Zones Work Understanding DST Timezone Abbreviations

External Resources

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