Does it account for Daylight Saving Time?

Yes, our converter uses the IANA timezone database, which includes all current DST rules for every timezone in the world.

UTC (Coordinated Universal Time) is the primary time standard by which the world regulates clocks. All timezones are defined as offsets from UTC.

Can I compare multiple timezones at once?

Yes, you can add multiple cities or timezones and see the equivalent times side by side.

How many timezones are there in the world?

There are 38 distinct UTC offsets in use, ranging from UTC-12 to UTC+14. This includes half-hour (UTC+5:30 India, UTC+9:30 Australia) and 45-minute offsets (UTC+5:45 Nepal, UTC+8:45 Australia).

What is the International Date Line?

The International Date Line (IDL) runs roughly along the 180° meridian in the Pacific Ocean. When you cross it westward, you gain a day; crossing eastward, you lose a day.

Why do some timezones have 30 or 45 minute offsets?

Countries chose offsets that best matched their solar noon. India uses UTC+5:30 and Nepal uses UTC+5:45 because standard hourly offsets didn't align well with their geography.

Which country has the most timezones?

France has the most (12 timezones) due to overseas territories. Russia spans 11 timezones. The US has 6 (including Hawaii and Alaska).

GMT to HST

-10h

GMT

GMTSOURCE

UTC+01:00☀ DST active

HH12

MM00

12:00 (24-hr)

12 AM6 AM12 PM6 PM12 AM

HST

UTC-10:00

HH02

MM00

02:00 (24-hr)

12 AM6 AM12 PM6 PM12 AM

Quick Reference

Time Conversion Table

GMT

HST

12:00 AM

1:00 PM-1

2:00 AM

3:00 PM-1

4:00 AM

5:00 PM-1

6:00 AM

7:00 PM-1

8:00 AM

9:00 PM-1

10:00 AM

11:00 PM-1

12:00 PM

1:00 AM

2:00 PM

3:00 AM

4:00 PM

5:00 AM

6:00 PM

7:00 AM

8:00 PM

9:00 AM

10:00 PM

11:00 AM

Green rows indicate typical business hours (9 AM - 5 PM)

GMT and HST on the World Map

The map below highlights the GMT (Greenwich Mean Time) and HST (Hawaii Standard Time) timezone regions across the globe.

GMT Zone

→

HST Zone

Explore all world timezones interactively →

GMT – Greenwich Mean Time

UTC+00:00

Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory in Greenwich, London. It is the same as UTC+00:00.

Countries in GMT

United KingdomIrelandIcelandPortugal (mainland)GhanaSenegalMaliMauritaniaGambiaGuineaSierra LeoneLiberiaIvory CoastBurkina FasoMorocco (historically)

Major Cities in GMT

LondonDublinLisbonAccraReykjavikEdinburghCasablancaDakarBamakoAbidjanConakryFreetownMonrovia

Key Facts about GMT

•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.

Daylight Saving:Yes – switches to BST

Learn more about GMT on Wikipedia

HST – Hawaii Standard Time

UTC-10:00

Hawaii Standard Time (HST) is the time zone for the Hawaiian Islands, 10 hours behind UTC.

Countries in HST

United States (Hawaii)

Major Cities in HST

HonoluluHiloKailuaPearl CityKapolei

Key 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.
•Hawaii is one of only two US states that don't observe DST (the other is Arizona).

Daylight Saving:No – UTC-10:00 year-round

Learn more about HST on Wikipedia

GMT to HST Time Difference – Complete Guide

GMT runs on Greenwich Mean Time (GMT) at UTC+00:00. HST runs on Hawaii Standard Time (HST) at UTC-10:00. That puts GMT 10 hours behind HST — a difference of -10h at the current offsets.

In practice, when it is 9:00 AM in GMT it is 11:00 PM in HST on the previous day. Midnight in GMT is 2:00 PM in HST. Neither zone observes daylight saving time, so the offset between them stays constant all year.

GMT to HST time conversion table

GMT (GMT)	HST (HST)	Day
12:00 AM	2:00 PM	previous day
6:00 AM	8:00 PM	previous day
7:00 AM	9:00 PM	previous day
8:00 AM	10:00 PM	previous day
9:00 AM	11:00 PM	previous day
12:00 PM	2:00 AM	same day
3:00 PM	5:00 AM	same day
5:00 PM	7:00 AM	same day
6:00 PM	8:00 AM	same day
9:00 PM	11:00 AM	same day

Why people convert GMT to HST time

Scheduling a call from GMT to HST: a 10:00 AM start in GMT lands at 12:00 AM in HST, so you can confirm the slot without doing the arithmetic yourself.
Handling a -10h gap: GMT and HST 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 HST is 11:00 PM in GMT.
Booking travel or deliveries: tracking HST local time against GMT keeps pickup windows and arrival estimates honest across the -10h offset.

Always state the zone abbreviation, not just the hour. "3:00 PM GMT" 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 GMT takes the early slot, the next week HST does.

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.

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.

Best time to call between GMT and HST

With a -10h offset there is no overlap inside a normal 9 AM – 5 PM day. HST opens at 9:00 AM HST, which is 11:00 PM in GMT, so real-time calls need an early-morning or late-evening slot on one side.

Business hours overlap

GMT and HST have no shared working hours because of the -10h gap. Teams need to alternate early starts or rely on asynchronous handovers.

GMT is 10 hours behind HST (GMT UTC+00:00 → HST UTC-10:00). 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

GMT

☀ Currently in DST

Standard: UTC+00:00 · DST: UTC+01:00

Clocks fall back on Sun, Oct 25, 2026

HST

Does not observe DST

Learn More About Time

Dive deeper into the fascinating world of timekeeping, time zones, and how they shape our global society:

⏳

History of Timekeeping

From sundials to atomic clocks - 5000 years of measuring time

🌍

How Time Zones Work

UTC, offsets, and why zones don't follow straight lines

☀️

Daylight Saving Time

DST dates, which countries observe it, and the ongoing debate

Frequently Asked Questions

What is the time difference between GMT and HST?

GMT (GMT, UTC+00:00) is 10 hours behind HST (HST, UTC-10:00). The gap is currently -10h.

How do I convert GMT time to HST time?

Add -10h to GMT local time. For example, 9:00 AM in GMT is 11:00 PM in HST (previous day).

What time is it in HST right now?

HST uses HST at UTC-10:00. Use the live converter at the top of this page — it updates in real time and already accounts for the -10h offset from GMT.

What is the best time to call HST from GMT?

There is no shared working-hours window because of the -10h gap. The closest option is 1:00 PM in GMT, which is 3:00 AM in HST.

Which is behind, GMT or HST?

GMT is 10 hours behind HST. When it is 12:00 PM in GMT it is 2:00 AM in HST.

Does daylight saving time affect the GMT–HST difference?

Neither zone observes daylight saving time, so the -10h offset between GMT and HST is fixed all year.

Which other cities share GMT's time zone?

GMT also covers London, Dublin, Lisbon, Accra, Reykjavik, Edinburgh, Casablanca, Dakar and 5 more.

Which countries use GMT, GMT's zone?

GMT is used in United Kingdom, Ireland, Iceland, Portugal (mainland), Ghana, Senegal, Mali, Mauritania and 7 more.

Is there a day difference between GMT and HST?

Not normally. The -10h gap only pushes the date over the previous day.

What is the time difference between GMT and HST?

HST is -10h from GMT.

What timezone is GMT in?

GMT operates on its local timezone.

What timezone is HST in?

HST operates on its local timezone.

Which countries use GMT (Greenwich Mean Time)?

GMT is used in United Kingdom, Ireland, Iceland, Portugal (mainland), Ghana, Senegal, and 9 more countries.

Does GMT observe daylight saving time?

Yes, GMT switches to BST during summer months.

What are some interesting facts about GMT?

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.