JST to KST Converter
Convert time between Japan Standard Time (JST) and Korea Standard Time (KST)
Japan Standard Time (JST)
Korea Standard Time (KST)
Time Difference
Korea Standard Time (KST) is 0 hours ahead of Japan Standard Time (JST)
Select Date
Select Time
Quick Reference
| JST | KST |
|---|---|
| 11:00 | 11:00 |
| 13:00 | 13:00 |
| 15:00 | 15:00 |
| 17:00 | 17:00 |
| 19:00 | 19:00 |
| 21:00 | 21:00 |
| 23:00 | 23:00 |
| 01:00 | 01:00 |
| 03:00 | 03:00 |
| 05:00 | 05:00 |
| 07:00 | 07:00 |
| 09:00 | 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 JST to KST Time Conversion
Converting time from Japan Standard Time (JST) to Korea Standard Time (KST) is the simplest cross-border conversion in East Asia: both share the UTC+9 offset, so JST and KST always show the same wall-clock time. Neither country observes daylight saving time, so this perfect alignment holds every day of the year.
Despite the matched clocks, the two regions remain distinct on holidays, fiscal calendars, and business customs. Whether you are coordinating with Tokyo, Osaka, Seoul, or Busan teams on tech, manufacturing, or media projects, the time component of scheduling is trivial — focus instead on calendar conventions and meeting etiquette.
Common Use Cases for JST to KST Conversion
Business & Work
- Coordinating regional headquarters operations between Japan and South Korea
- Scheduling joint product launches, releases, or trading windows between the two countries
- Running shared standups for cross-border engineering, gaming, or content teams
Personal & Travel
- Keeping in touch with family or friends living in South Korea
- Planning short flights from Japan to Seoul, Busan, or Jeju
- Scheduling online study, K-content/J-content watch parties, or virtual events
Time Zone Information
Japan Standard Time (JST)
- UTC Offset: UTC+9 (no DST observed)
- IANA Timezone: Asia/Tokyo
- Daylight Saving: Japan does not observe daylight saving time
- Major Cities: Tokyo, Osaka, Kyoto, Yokohama, Nagoya, Sapporo, Fukuoka
- Coverage: All of Japan
Korea Standard Time (KST)
- UTC Offset: UTC+9 (no DST observed)
- IANA Timezone: Asia/Seoul
- Daylight Saving: South Korea does not observe daylight saving time
- Major Cities: Seoul, Busan, Incheon, Daegu, Daejeon, Gwangju, Jeju
- Coverage: All of South Korea
Quick Reference: JST to KST
Remember: JST and KST are identical (both UTC+9). Neither region observes daylight saving time, so this alignment holds year-round.
Frequently Asked Questions
What is the time difference between JST and KST?
There is no time difference. Japan Standard Time (JST) and Korea Standard Time (KST) both use the UTC+9 offset, so 12:00 PM in Tokyo is also 12:00 PM in Seoul.
Does the JST to KST time difference change throughout the year?
No. Neither Japan nor South Korea observes daylight saving time, so JST and KST stay perfectly aligned every day of the year.
Why did Korea once consider changing KST?
KST was briefly UTC+8:30 (Pyongyang Time was used during the colonial period and was reintroduced in North Korea from 2015 to 2018). South Korea has stayed on UTC+9 since 1961, matching JST exactly. Today both regions are firmly on UTC+9.
Are business calendars the same between Japan and Korea?
Local clocks match, but business calendars do not. Japan observes Golden Week and Obon; Korea observes Lunar New Year (Seollal) and Chuseok. Plan around each country's holiday weeks even when scheduling at identical times.
Which regions and cities use KST?
KST (UTC+9) is used by all of South Korea. Major cities include Seoul, Busan, Incheon, Daegu, Daejeon, Gwangju, and Jeju.
Which regions use JST?
JST (UTC+9) is used by all of Japan. Major cities include Tokyo, Osaka, Kyoto, Yokohama, Nagoya, Sapporo, and Fukuoka.
Pro Tips
- • JST and KST are identical — no conversion needed for the time itself.
- • Neither region observes DST, so this alignment is constant year-round.
- • Calendar differences matter more than clock differences: check Japanese and Korean public holidays before scheduling.
- • A single meeting time can serve Tokyo, Osaka, Seoul, and Busan teams at once — useful for regional standups.
- • Both countries observe similar working hours (roughly 9 AM to 6 PM), so traditional business windows align naturally.
- • Flights between Tokyo and Seoul are short (about 2.5 hours) and produce no jet lag, since the clocks already match.