AST to KST Converter
Convert time between Atlantic Standard Time (AST) and Korea Standard Time (KST)
Atlantic Standard Time (AST)
Korea Standard Time (KST)
Time Difference
Korea Standard Time (KST) is 0 hours ahead of Atlantic Standard Time (AST)
Select Date
Select Time
Quick Reference
| AST | KST |
|---|---|
| 23:00 | 11:00 |
| 01:00 | 13:00 |
| 03:00 | 15:00 |
| 05:00 | 17:00 |
| 07:00 | 19:00 |
| 09:00 | 21:00 |
| 11:00 | 23:00 |
| 13:00 | 01:00 |
| 15:00 | 03:00 |
| 17:00 | 05:00 |
| 19:00 | 07:00 |
| 21:00 | 09:00 |
Top 10 Most Common Time Zones
| Abbreviation | Full Name | UTC Offset | Typical Use |
|---|---|---|---|
| UTC | Coordinated Universal Time | UTC ±0 | Global reference standard (servers, logs, APIs) |
| EST / EDT | Eastern (US) Time | UTC −5 / −4 | New York, Toronto — North American business hub |
| CST / CDT | Central (US) Time | UTC −6 / −5 | Chicago, Dallas — US central business region |
| PST / PDT | Pacific (US) Time | UTC −8 / −7 | San Francisco, Los Angeles — tech industry standard |
| GMT / BST | Greenwich Mean / British Summer Time | UTC 0 / +1 | UK, used globally as a reference with UTC |
| CET / CEST | Central European (Summer) Time | UTC +1 / +2 | Paris, Berlin, Amsterdam — EU business core |
| IST | India Standard Time | UTC +5:30 | India — major IT & outsourcing region |
| CST | China Standard Time | UTC +8 | Beijing, Shanghai — East Asia business hub |
| JST | Japan Standard Time | UTC +9 | Tokyo — finance & tech hub |
| AEST / AEDT | Australian Eastern (Daylight) Time | UTC +10 / +11 | Sydney, Melbourne — APAC regional business |
Why Time Zone Abbreviations Are Ambiguous
Unlike standardized identifiers (like America/New_York or Europe/London from the IANA tz database), abbreviations such as "CST" or "IST" are not globally unique. They can refer to different time zones depending on context — country, region, or even time of year (due to daylight saving time).
Common Ambiguous Time Zone Abbreviations
| Abbrev. | Common Meaning(s) | UTC Offset | Region(s) |
|---|---|---|---|
| CST | Central Standard Time / China Standard Time / Cuba Standard Time | UTC−6 / UTC+8 / UTC−5 | North America, China, Cuba |
| IST | Indian Standard Time / Irish Standard Time / Israel Standard Time | UTC+5:30 / UTC+1 / UTC+2 | India, Ireland, Israel |
| AST | Atlantic Standard Time / Arabia Standard Time | UTC−4 / UTC+3 | Caribbean, Canada, Middle East |
| PST | Pacific Standard Time / Philippine Standard Time | UTC−8 / UTC+8 | North America, Philippines |
| EST | Eastern Standard Time (North America / Australia) | UTC−5 / UTC+10 | North America, Australia |
✅ Best Practice
To avoid ambiguity, always:
- Use IANA tz identifiers — e.g.,
America/New_Yorkinstead of "EST" - Specify UTC offset explicitly — e.g.,
UTC−5when abbreviations must be used - Include the full timezone name — e.g., "Eastern Standard Time (EST)" with UTC offset
About AST to KST Time Conversion
Converting time between Atlantic Standard Time (AST) and Korea Standard Time (KST) bridges Halifax, Charlottetown, San Juan and Bermuda with Seoul, Busan, Incheon and Daegu. AST is UTC-4 while KST is UTC+9, placing KST 13 hours ahead of AST. The two regions sit roughly half a day apart, so most coordination relies on async handoffs rather than live meetings.
This converter uses the IANA timezone database to handle daylight saving transitions automatically. AST is observed in the Maritimes from early November to mid-March; outside that window the region uses ADT (UTC-3), narrowing the offset to KST to 12 hours. South Korea does not observe daylight saving, so KST stays at UTC+9 year-round. Bermuda and Puerto Rico keep AST all year — no DST changes — making the 13-hour offset constant for those locations.
Common Use Cases for AST to KST Conversion
Business & Work
- Scheduling handoffs between Halifax-area teams and South Korean partners during the northern winter
- Coordinating shipping, manufacturing and supply-chain operations between the Maritimes and Korea
- Planning research, finance and engineering work between Atlantic Canada or the Caribbean and Seoul
Personal & Travel
- Planning travel itineraries between the Atlantic region and South Korea
- Coordinating with family and friends in Seoul, Busan, Incheon or Daegu from Halifax, San Juan or Bermuda
- Scheduling virtual events and online classes for AST and KST audiences
Time Zone Information
Atlantic Standard Time (AST)
- UTC Offset: UTC-4
- IANA Timezone: America/Halifax
- Daylight Saving: Early November to mid-March (Maritimes); Bermuda and Puerto Rico stay on AST year-round
- Major Cities: Halifax, Charlottetown, San Juan, Hamilton (Bermuda)
- Coverage: Atlantic Canada (winter), Bermuda and Puerto Rico (year-round)
Korea Standard Time (KST)
- UTC Offset: UTC+9
- IANA Timezone: Asia/Seoul
- Daylight Saving: None - KST is observed year-round
- Major Cities: Seoul, Busan, Incheon, Daegu, Daejeon, Gwangju
- Coverage: All of South Korea
Quick Reference: AST to KST
Remember: KST is always 13 hours ahead of AST during the northern winter
Frequently Asked Questions
What is the time difference between AST and KST?
Atlantic Standard Time (AST) is UTC-4, while Korea Standard Time (KST) is UTC+9. KST is 13 hours ahead of AST. When it is 6:00 PM in Halifax, it is 7:00 AM the next day in Seoul.
When does this AST to KST conversion apply?
The Maritimes (Halifax, Charlottetown, etc.) observe AST from early November to mid-March; outside that window they use ADT (UTC-3), narrowing the offset to KST to 12 hours. Bermuda and Puerto Rico stay on AST year-round, so the 13-hour offset to Seoul holds in every season for those locations.
How does the time difference change throughout the year?
KST is constant at UTC+9. The variation comes from the Atlantic side: AST (UTC-4) gives a 13-hour gap, ADT (UTC-3) gives a 12-hour gap. The transition happens twice a year in the Maritimes — early November and mid-March. Bermuda and Puerto Rico stay at the 13-hour offset all year.
What are the best times for AST-KST business calls?
The 13-hour gap means morning AST corresponds to late evening KST and afternoon AST aligns with early-morning-next-day KST. 6:00 PM AST is 7:00 AM next-day KST — a workable handoff for an end-of-day Halifax call to a Seoul morning. Same-day live meetings during business hours on both sides are difficult.
Which countries/regions use KST timezone?
KST is used across all of South Korea. Major cities include Seoul, Busan, Incheon, Daegu, Daejeon, and Gwangju. South Korea does not observe daylight saving, so KST is the same year-round.
Which countries/regions use AST timezone?
AST is observed in Atlantic Canada (Nova Scotia, New Brunswick, Prince Edward Island, parts of Labrador) during winter, and year-round in Bermuda and Puerto Rico. Major AST cities include Halifax, Charlottetown, San Juan, and Hamilton (Bermuda).
Pro Tips
- • KST is 13 hours ahead of AST — add 13 hours to a Halifax time to get the Seoul time (most results land on the next day).
- • Korea has no daylight saving. The 13-hour offset only applies during AST (November–March in the Maritimes); in ADT it narrows to 12 hours.
- • Best handoff window: 6:00 PM–9:00 PM AST equals 7:00 AM–10:00 AM next-day KST — end-of-day Halifax hands off to morning Seoul.
- • Bermuda and Puerto Rico stay on AST year-round, so the 13-hour offset to Seoul is constant for those locations.
- • Use IANA identifiers (America/Halifax and Asia/Seoul) in calendars so the AST/ADT switch is handled automatically.
- • Live same-day business-hour meetings are impractical due to the 13-hour gap; design async workflows or recorded standups instead.