South Korea to AST
-13hSouth Korea
KSTSOURCEAST
ASTGreen rows indicate typical business hours (9 AM - 5 PM)
KST and AST on the World Map
The map below highlights the KST (Korea Standard Time) and AST (Atlantic Standard Time) timezone regions across the globe.
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).
AST – Atlantic Standard Time
UTC-04:00Atlantic Standard Time (AST) is the time zone for the Canadian Atlantic provinces and the Caribbean, 4 hours behind UTC.
- •Puerto Rico uses AST year-round and does not observe DST.
- •AST is 1 hour ahead of EST.
- •Halifax, the capital of Nova Scotia, is the largest city in AST Canada.
Time Conversion Guide: South Korea to AST
South Korea runs on Korean Standard Time (KST) at UTC+09:00. AST runs on Atlantic Standard Time (AST) at UTC-04:00. That puts South Korea 13 hours behind AST — a difference of -13h at the current offsets.
In practice, when it is 9:00 AM in South Korea it is 8:00 PM in AST on the previous day. Midnight in South Korea is 11:00 AM in AST. Neither zone observes daylight saving time, so the offset between them stays constant all year.
South Korea to AST time conversion table
| South Korea (KST) | AST (AST) | Day |
|---|---|---|
| 12:00 AM | 11:00 AM | previous day |
| 6:00 AM | 5:00 PM | previous day |
| 7:00 AM | 6:00 PM | previous day |
| 8:00 AM | 7:00 PM | previous day |
| 9:00 AM | 8:00 PM | previous day |
| 12:00 PM | 11:00 PM | previous day |
| 3:00 PM | 2:00 AM | same day |
| 5:00 PM | 4:00 AM | same day |
| 6:00 PM | 5:00 AM | same day |
| 9:00 PM | 8:00 AM | same day |
Why people convert South Korea to AST time
- Scheduling a call from South Korea to AST: a 10:00 AM start in South Korea lands at 9:00 PM in AST the previous day, so you can confirm the slot without doing the arithmetic yourself.
- Handling a -13h gap: South Korea and AST 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 AST is 8:00 PM in South Korea.
- Keeping family and friends in sync: knowing that 8:00 PM in South Korea is 7:00 AM in AST makes it easy to avoid calling at 3 AM.
- Always state the zone abbreviation, not just the hour. "3:00 PM KST" is unambiguous; "3 PM" across a -13h gap is not.
- With a -13h gap there is no shared 9-to-5 window, so alternate the early start: one week South Korea takes the early slot, the next week AST does.
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.
About AST (Atlantic Standard Time)
Atlantic Standard Time (AST) covers Canada's Atlantic provinces (Nova Scotia, New Brunswick, Prince Edward Island, and most of Labrador), as well as several Caribbean nations. Puerto Rico and the US Virgin Islands use AST year-round without daylight saving time. The Canadian provinces switch to Atlantic Daylight Time (ADT) in summer.
Best time to call between South Korea and AST
With a -13h offset there is no overlap inside a normal 9 AM – 5 PM day. AST opens at 9:00 AM AST, which is 8:00 PM in South Korea, so real-time calls need an early-morning or late-evening slot on one side.
Business hours overlap
South Korea and AST have no shared working hours because of the -13h gap. Teams need to alternate early starts or rely on asynchronous handovers.
South Korea is 13 hours behind AST (KST UTC+09:00 → AST UTC-04:00). 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
South Korea
Does not observe DST
AST
☀ Currently in DST
Standard: UTC-04:00 · DST: UTC-03:00
Clocks fall back on Sun, Nov 1, 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 South Korea and AST?
South Korea (KST, UTC+09:00) is 13 hours behind AST (AST, UTC-04:00). The gap is currently -13h.
How do I convert South Korea time to AST time?
Add -13h to South Korea local time. For example, 9:00 AM in South Korea is 8:00 PM in AST (previous day).
What time is it in AST right now?
AST uses AST at UTC-04:00. Use the live converter at the top of this page — it updates in real time and already accounts for the -13h offset from South Korea.
What is the best time to call AST from South Korea?
There is no shared working-hours window because of the -13h gap. The closest option is 1:00 PM in South Korea, which is 12:00 AM in AST.
Which is behind, South Korea or AST?
South Korea is 13 hours behind AST. When it is 12:00 PM in South Korea it is 11:00 PM in AST.
Do South Korea and AST use different time zones?
South Korea (South Korea) uses KST at UTC+09:00, while AST uses AST at UTC-04:00. The IANA identifiers are Asia/Seoul and America/Halifax.
Does daylight saving time affect the South Korea–AST difference?
Neither zone observes daylight saving time, so the -13h offset between South Korea and AST is fixed all year.
Which other cities share South Korea's time zone?
KST also covers Seoul, Busan, Incheon, Daegu, Daejeon, Pyongyang.
Which countries use KST, South Korea's zone?
KST is used in South Korea, North Korea.
Is there a day difference between South Korea and AST?
Sometimes. The -13h gap is large enough that 8:00 PM or later in South Korea already falls on the in AST.
What is the time difference between South Korea and AST?
AST is -13h from South Korea.
What timezone is South Korea in?
South Korea operates on its local timezone.
What timezone is AST in?
AST operates on its local timezone.
Which countries use KST (Korea Standard Time)?
KST is used in South Korea, North Korea.
Does KST observe daylight saving time?
No, KST does not observe daylight saving time and remains at UTC+09:00 year-round.
What are some interesting facts about KST?
South Korea does not observe daylight saving time. Seoul is home to Samsung, LG, and Hyundai headquarters.
Which cities are in the AST timezone?
Major cities in the AST timezone include Halifax, San Juan, Santo Domingo, Caracas, La Paz, Fredericton, Charlottetown.
What is the UTC offset for AST?
Atlantic Standard Time (AST) is at UTC-04:00. During daylight saving time, it shifts to ADT.
What should I know about the AST timezone?
Puerto Rico uses AST year-round and does not observe DST. AST is 1 hour ahead of EST.
When is it midnight in South Korea, what time is it in AST?
When it is 12:00 AM (midnight) in South Korea (KST), it is -13h later in AST (AST).
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