HST to Seoul
+19hHST
HSTSOURCESeoul
KSTGreen rows indicate typical business hours (9 AM - 5 PM)
HST and KST on the World Map
The map below highlights the HST (Hawaii Standard Time) and KST (Korea Standard 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).
KST – Korea Standard Time
UTC+09:00Korea Standard Time (KST) is the time zone for South Korea, 9 hours ahead of UTC.
- •South Korea does not observe daylight saving time.
- •Seoul is home to Samsung, LG, and Hyundai headquarters.
- •KST is the same offset as JST (UTC+09:00).
About Seoul
WikipediaSeoul operates on Korea Standard Time (KST), UTC+9, same as Japan. As a global tech and entertainment hub, Seoul coordinates with East Asian markets.
Seoul has the fastest average internet speed in the world.
Comparing Time Zones: HST and Seoul
HST runs on Hawaii Standard Time (HST) at UTC-10:00. Seoul runs on Korean Standard Time (KST) at UTC+09:00. That puts HST 19 hours ahead of Seoul — a difference of +19h at the current offsets.
In practice, when it is 9:00 AM in HST it is 4:00 AM in Seoul on the next day. Midnight in HST is 7:00 PM in Seoul. Neither zone observes daylight saving time, so the offset between them stays constant all year.
HST to Seoul time conversion table
| HST (HST) | Seoul (KST) | Day |
|---|---|---|
| 12:00 AM | 7:00 PM | same day |
| 6:00 AM | 1:00 AM | next day |
| 7:00 AM | 2:00 AM | next day |
| 8:00 AM | 3:00 AM | next day |
| 9:00 AM | 4:00 AM | next day |
| 12:00 PM | 7:00 AM | next day |
| 3:00 PM | 10:00 AM | next day |
| 5:00 PM | 12:00 PM | next day |
| 6:00 PM | 1:00 PM | next day |
| 9:00 PM | 4:00 PM | next day |
Why people convert HST to Seoul time
- Scheduling a call from HST to Seoul: a 10:00 AM start in HST lands at 5:00 AM in Seoul the next day, so you can confirm the slot without doing the arithmetic yourself.
- Handling a +19h gap: HST and Seoul 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 Seoul is 4:00 AM in HST.
- Watching a live event or market open: HST viewers need 4:00 AM in Seoul to catch a 9:00 AM start there, and 5:00 AM 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 +19h gap is not.
- With a +19h gap there is no shared 9-to-5 window, so alternate the early start: one week HST takes the early slot, the next week Seoul 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 KST (Korea Standard Time)
Korea Standard Time (KST) is the time zone used in South Korea. It shares the same UTC offset as Japan Standard Time but is a distinct time zone. South Korea does not observe daylight saving time. Seoul, the capital, is a major global tech and business hub.
Best time to call between HST and Seoul
With a +19h offset there is no overlap inside a normal 9 AM – 5 PM day. Seoul opens at 9:00 AM KST, which is 4:00 AM in HST, so real-time calls need an early-morning or late-evening slot on one side.
Business hours overlap
HST and Seoul have no shared working hours because of the +19h gap. Teams need to alternate early starts or rely on asynchronous handovers.
HST is 19 hours ahead of Seoul (HST UTC-10:00 → KST UTC+09:00). There is no shared 9-to-5 window, so plan around an early or late slot. Remember to re-check around daylight-saving transitions.
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 Seoul?
HST (HST, UTC-10:00) is 19 hours ahead of Seoul (KST, UTC+09:00). The gap is currently +19h.
How do I convert HST time to Seoul time?
Add +19h to HST local time. For example, 9:00 AM in HST is 4:00 AM in Seoul (next day).
What time is it in Seoul right now?
Seoul uses KST at UTC+09:00. Use the live converter at the top of this page — it updates in real time and already accounts for the +19h offset from HST.
What is the best time to call Seoul from HST?
There is no shared working-hours window because of the +19h gap. The closest option is 1:00 PM in HST, which is 8:00 AM in Seoul.
Which is ahead, HST or Seoul?
HST is 19 hours ahead of Seoul. When it is 12:00 PM in HST it is 7:00 AM in Seoul.
Do HST and Seoul use different time zones?
HST uses HST at UTC-10:00, while Seoul (South Korea) uses KST at UTC+09:00. The IANA identifiers are Pacific/Honolulu and Asia/Seoul.
Does daylight saving time affect the HST–Seoul difference?
Neither zone observes daylight saving time, so the +19h offset between HST and Seoul 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 Seoul?
Sometimes. The +19h gap is large enough that 8:00 PM or later in HST already falls on the next day in Seoul.
What is the time difference between HST and Seoul?
Seoul is +19h from HST.
What timezone is HST in?
HST operates on its local timezone.
What timezone is Seoul in?
Seoul operates on Korea Standard Time (KST), UTC+9, same as Japan. As a global tech and entertainment hub, Seoul coordinates with East Asian markets.
What are the business hours in Seoul?
Standard business hours in Seoul are 9:00 AM - 6:00 PM KST.
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 KST timezone?
Major cities in the KST timezone include Seoul, Busan, Incheon, Daegu, Daejeon, Pyongyang.
What is the UTC offset for KST?
Korea Standard Time (KST) is at UTC+09:00.
What should I know about the KST timezone?
South Korea does not observe daylight saving time. Seoul is home to Samsung, LG, and Hyundai headquarters.
When is it midnight in HST, what time is it in Seoul?
When it is 12:00 AM (midnight) in HST (HST), it is +19h later in Seoul (KST).
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