HST to GMT
+10hHST
HSTSOURCEGMT
GMTGreen rows indicate typical business hours (9 AM - 5 PM)
HST and GMT on the World Map
The map below highlights the HST (Hawaii Standard Time) and GMT (Greenwich Mean Time) timezone regions across the globe.
HST – Hawaii Standard Time
UTC-10:00Hawaii Standard Time (HST) is the time zone for the Hawaiian Islands, 10 hours behind UTC.
- •Hawaii does not observe daylight saving time.
- •HST is 5 hours behind EST in winter and 6 hours behind EDT in summer.
- •Hawaii is one of only two US states that don't observe DST (the other is Arizona).
GMT – Greenwich Mean Time
UTC+00:00Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory in Greenwich, London. It is the same as UTC+00:00.
- •GMT is based on the Prime Meridian (0° longitude) passing through Greenwich, London.
- •The Royal Observatory in Greenwich has been the reference point for GMT since 1884.
- •GMT and UTC are often used interchangeably, but UTC is based on atomic clocks.
- •Iceland uses GMT year-round and never observes daylight saving time.
- •The UK switches from GMT to BST (British Summer Time) in late March each year.
HST to GMT Time Difference – Complete Guide
HST runs on Hawaii Standard Time (HST) at UTC-10:00. GMT runs on Greenwich Mean Time (GMT) at UTC+00:00. That puts HST 10 hours ahead of GMT — a difference of +10h at the current offsets.
In practice, when it is 9:00 AM in HST it is 7:00 PM in GMT. Midnight in HST is 10:00 AM in GMT. Neither zone observes daylight saving time, so the offset between them stays constant all year.
HST to GMT time conversion table
| HST (HST) | GMT (GMT) | Day |
|---|---|---|
| 12:00 AM | 10:00 AM | same day |
| 6:00 AM | 4:00 PM | same day |
| 7:00 AM | 5:00 PM | same day |
| 8:00 AM | 6:00 PM | same day |
| 9:00 AM | 7:00 PM | same day |
| 12:00 PM | 10:00 PM | same day |
| 3:00 PM | 1:00 AM | next day |
| 5:00 PM | 3:00 AM | next day |
| 6:00 PM | 4:00 AM | next day |
| 9:00 PM | 7:00 AM | next day |
Why people convert HST to GMT time
- Scheduling a call from HST to GMT: a 10:00 AM start in HST lands at 8:00 PM in GMT, so you can confirm the slot without doing the arithmetic yourself.
- Handling a +10h gap: HST and GMT have no overlap inside a normal 9-to-5 day, so real-time meetings need an early-morning or late-evening slot on one side. 9:00 AM in GMT is 7:00 PM in HST.
- Watching a live event or market open: HST viewers need 7:00 PM in GMT to catch a 9:00 AM start there, and 2:00 PM if the event is anchored to HST.
- Always state the zone abbreviation, not just the hour. "3:00 PM HST" is unambiguous; "3 PM" across a +10h gap is not.
- With a +10h gap there is no shared 9-to-5 window, so alternate the early start: one week HST takes the early slot, the next week GMT does.
About HST (Hawaii Standard Time)
Hawaii Standard Time (HST) is used in the state of Hawaii and does not observe daylight saving time. This makes HST one of the most consistent time zones in the US. The Hawaiian Islands are among the last places on Earth to see a new calendar day.
About GMT (Greenwich Mean Time)
Greenwich Mean Time (GMT) is the clock time at the Royal Observatory in Greenwich, London, which sits on the Prime Meridian (0° longitude). GMT serves as the reference point from which all other time zones are calculated. The United Kingdom uses GMT during winter months and switches to British Summer Time (BST, UTC+01:00) from late March to late October. Several West African nations use GMT year-round. GMT is often used interchangeably with UTC (Coordinated Universal Time), although technically they are different – UTC is based on atomic clocks while GMT is based on Earth's rotation.
Best time to call between HST and GMT
With a +10h offset there is no overlap inside a normal 9 AM – 5 PM day. GMT opens at 9:00 AM GMT, which is 7:00 PM in HST, so real-time calls need an early-morning or late-evening slot on one side.
Business hours overlap
HST and GMT have no shared working hours because of the +10h gap. Teams need to alternate early starts or rely on asynchronous handovers.
HST is 10 hours ahead of GMT (HST UTC-10:00 → GMT UTC+00:00). There is no shared 9-to-5 window, so plan around an early or late slot. Remember to re-check around daylight-saving transitions.
🕐 Daylight Saving Time Info
HST
Does not observe DST
GMT
☀ Currently in DST
Standard: UTC+00:00 · DST: UTC+01:00
Clocks fall back on Sun, Oct 25, 2026
Learn More About Time
Dive deeper into the fascinating world of timekeeping, time zones, and how they shape our global society:
Frequently Asked Questions
What is the time difference between HST and GMT?
HST (HST, UTC-10:00) is 10 hours ahead of GMT (GMT, UTC+00:00). The gap is currently +10h.
How do I convert HST time to GMT time?
Add +10h to HST local time. For example, 9:00 AM in HST is 7:00 PM in GMT.
What time is it in GMT right now?
GMT uses GMT at UTC+00:00. Use the live converter at the top of this page — it updates in real time and already accounts for the +10h offset from HST.
What is the best time to call GMT from HST?
There is no shared working-hours window because of the +10h gap. The closest option is 1:00 PM in HST, which is 11:00 PM in GMT.
Which is ahead, HST or GMT?
HST is 10 hours ahead of GMT. When it is 12:00 PM in HST it is 10:00 PM in GMT.
Does daylight saving time affect the HST–GMT difference?
Neither zone observes daylight saving time, so the +10h offset between HST and GMT is fixed all year.
Which other cities share HST's time zone?
HST also covers Honolulu, Hilo, Kailua, Pearl City, Kapolei.
Which countries use HST, HST's zone?
HST is used in United States (Hawaii).
Is there a day difference between HST and GMT?
Not normally. The +10h gap only pushes the date over for late-evening times.
What is the time difference between HST and GMT?
GMT is +10h from HST.
What timezone is HST in?
HST operates on its local timezone.
What timezone is GMT in?
GMT operates on its local timezone.
Which countries use HST (Hawaii Standard Time)?
HST is used in United States (Hawaii).
Does HST observe daylight saving time?
No, HST does not observe daylight saving time and remains at UTC-10:00 year-round.
What are some interesting facts about HST?
Hawaii does not observe daylight saving time. HST is 5 hours behind EST in winter and 6 hours behind EDT in summer.
Which cities are in the GMT timezone?
Major cities in the GMT timezone include London, Dublin, Lisbon, Accra, Reykjavik, Edinburgh, Casablanca, Dakar.
What is the UTC offset for GMT?
Greenwich Mean Time (GMT) is at UTC+00:00. During daylight saving time, it shifts to BST.
What should I know about the GMT timezone?
GMT is based on the Prime Meridian (0° longitude) passing through Greenwich, London. The Royal Observatory in Greenwich has been the reference point for GMT since 1884.
When is it midnight in HST, what time is it in GMT?
When it is 12:00 AM (midnight) in HST (HST), it is +10h later in GMT (GMT).
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