KST to JST Converter (Korea Time to Japan Time)

JST and KST show the same time.

Seoul and Tokyo share the same clock. South Korea (KST) and Japan (JST) are both on UTC+9, neither country uses daylight saving time today, and the difference between the two cities is zero in every month of the year. A meeting at 3 p.m. in Tokyo is a meeting at 3 p.m. in Seoul.

The match is a legacy of history. Japan fixed its national standard time on the 135th meridian east, which passes through the city of Akashi, and Korea has used the same offset for most of the period since 1912. For about seven years in the 1950s and 1960s Korea ran half an hour behind Japan, at UTC+8:30, until it returned to UTC+9 in 1961.

How to use this tool

1. Pick a date and time in KST. The date matters when daylight saving time is in force.
2. Read the matching time in JST, with both UTC offsets.
3. Use "Use current time" for now, or the tables below for a quick look.

Formula

JST time = KST time − (KST UTC offset) + (JST UTC offset)

The converter looks up both UTC offsets for the actual instant in the saved IANA time zone rules, so daylight saving changes are included automatically.

Example

Worked with the saved rules:

9:00 AM KST on March 2, 2026 = 9:00 AM JST

6:30 PM KST on August 3, 2026 = 6:30 PM JST

Time difference through the year

The difference depends on the date when either place moves its clocks. These are the offsets on two reference days, from the saved IANA rules:

Clock changes in 2026

Korea Standard Time and Japan Standard Time do not change clocks in this year, so the difference stays the same all year.

KST to JST time table

Each hour in Korea Standard Time with the matching Japan Standard Time time.

JST to KST time table

Each hour in Japan Standard Time with the matching Korea Standard Time time.

Hours that work in both places

Hours (on the January reference day) that fall between 8:00 AM and 8:00 PM in both KST and JST:

How the two clocks diverged and converged

Japan adopted a single standard time in 1888, based on the 135° meridian. Korea followed the same time while under Japanese rule and, after independence, switched in 1954 to a time based on its own central meridian, 127.5°E, which is UTC+8:30. That ended on August 10, 1961, when South Korea went back to UTC+9.

Both countries have also tried daylight saving time. Japan used it during the occupation, from 1948 to 1951, and South Korea last used it in 1987 and 1988 around the Seoul Olympics. Neither country has used it since. North Korea has been on UTC+9 as well since May 2018, after a three-year spell at UTC+8:30.

Travel and business between the two cities

With no time difference, there is no jet lag between Seoul and Tokyo, and flights between Incheon or Gimpo and Haneda or Narita take about two hours. Meetings can start at the same local hour, and schedules, train tickets and webinars quoted in either country need no conversion.

The clocks match, but the calendars do not. Japan's Golden Week falls in late April and early May and Obon in mid-August, while Korea's holidays include Seollal and Chuseok, which follow the lunar calendar. Check each country's holiday list before you set a deadline.