Asia/Seoul

Time zone identifier: Asia/Seoul

Current civil offset: +09:00 (KST)

Current DST state: Observing Standard Time

First standard time adoption: Adopted on 1908-03-31

Local Mean Time (LMT): +08:27:52 based on geographic meridian

Total recorded transitions: 29 transitions across 5 distinct offsets

Associated countries: KR

Aliases (Link targets): ROK

Historical Offset Step Chart (1880 to Present)

Text summary: Asia/Seoul shifted between 5 distinct offsets from 1908-03-31 through the modern era.

Complete Transition History (29 Transitions)

UTC Instant	Local Wall Time	Shift	Abbreviation	DST	Effect
`1908-03-31T15:32:08Z`	`1908-04-01 00:02:08`	+08:27:52 → +08:30	`KST`	No	gap
`1911-12-31T15:30:00Z`	`1912-01-01 00:30:00`	+08:30 → +09:00	`JST`	No	gap
`1945-09-07T15:00:00Z`	`1945-09-08 00:00:00`	+09:00 → +09:00	`KST`	No	offset-only
`1948-05-31T15:00:00Z`	`1948-06-01 01:00:00`	+09:00 → +10:00	`KDT`	Yes	gap
`1948-09-12T14:00:00Z`	`1948-09-12 23:00:00`	+10:00 → +09:00	`KST`	No	overlap
`1949-04-02T15:00:00Z`	`1949-04-03 01:00:00`	+09:00 → +10:00	`KDT`	Yes	gap
`1949-09-10T14:00:00Z`	`1949-09-10 23:00:00`	+10:00 → +09:00	`KST`	No	overlap
`1950-03-31T15:00:00Z`	`1950-04-01 01:00:00`	+09:00 → +10:00	`KDT`	Yes	gap
`1950-09-09T14:00:00Z`	`1950-09-09 23:00:00`	+10:00 → +09:00	`KST`	No	overlap
`1951-05-05T15:00:00Z`	`1951-05-06 01:00:00`	+09:00 → +10:00	`KDT`	Yes	gap
`1951-09-08T14:00:00Z`	`1951-09-08 23:00:00`	+10:00 → +09:00	`KST`	No	overlap
`1954-03-20T15:00:00Z`	`1954-03-20 23:30:00`	+09:00 → +08:30	`KST`	No	overlap
`1955-05-04T15:30:00Z`	`1955-05-05 01:00:00`	+08:30 → +09:30	`KDT`	Yes	gap
`1955-09-08T14:30:00Z`	`1955-09-08 23:00:00`	+09:30 → +08:30	`KST`	No	overlap
`1956-05-19T15:30:00Z`	`1956-05-20 01:00:00`	+08:30 → +09:30	`KDT`	Yes	gap
`1956-09-29T14:30:00Z`	`1956-09-29 23:00:00`	+09:30 → +08:30	`KST`	No	overlap
`1957-05-04T15:30:00Z`	`1957-05-05 01:00:00`	+08:30 → +09:30	`KDT`	Yes	gap
`1957-09-21T14:30:00Z`	`1957-09-21 23:00:00`	+09:30 → +08:30	`KST`	No	overlap
`1958-05-03T15:30:00Z`	`1958-05-04 01:00:00`	+08:30 → +09:30	`KDT`	Yes	gap
`1958-09-20T14:30:00Z`	`1958-09-20 23:00:00`	+09:30 → +08:30	`KST`	No	overlap
`1959-05-02T15:30:00Z`	`1959-05-03 01:00:00`	+08:30 → +09:30	`KDT`	Yes	gap
`1959-09-19T14:30:00Z`	`1959-09-19 23:00:00`	+09:30 → +08:30	`KST`	No	overlap
`1960-04-30T15:30:00Z`	`1960-05-01 01:00:00`	+08:30 → +09:30	`KDT`	Yes	gap
`1960-09-17T14:30:00Z`	`1960-09-17 23:00:00`	+09:30 → +08:30	`KST`	No	overlap
`1961-08-09T15:30:00Z`	`1961-08-10 00:30:00`	+08:30 → +09:00	`KST`	No	gap
`1987-05-09T17:00:00Z`	`1987-05-10 03:00:00`	+09:00 → +10:00	`KDT`	Yes	gap
`1987-10-10T17:00:00Z`	`1987-10-11 02:00:00`	+10:00 → +09:00	`KST`	No	overlap
`1988-05-07T17:00:00Z`	`1988-05-08 03:00:00`	+09:00 → +10:00	`KDT`	Yes	gap
`1988-10-08T17:00:00Z`	`1988-10-09 02:00:00`	+10:00 → +09:00	`KST`	No	overlap

Notes from the Maintainers

Source: asia (Lines 2671 to 2720)

From Paul Eggert (2016-08-23):
The Korean Wikipedia entry gives the following sources for UT offsets:

1908: Official Journal Article No. 3994 (decree No. 5)
1912: Governor-General of Korea Official Gazette Issue No. 367
(Announcement No. 338)
1954: Presidential Decree No. 876 (1954-03-17)
1961: Law No. 676 (1961-08-07)

(Another source "1987: Law No. 3919 (1986-12-31)" was in the 2014-10-30
edition of the Korean Wikipedia entry.)

I guessed that time zone abbreviations through 1945 followed the same
rules as discussed under Taiwan, with nominal switches from JST to KST
when the respective cities were taken over by the Allies after WWII.

For Pyongyang, guess no changes from World War II until 2015, as we
have no information otherwise.

From Steffen Thorsen (2015-08-07):
According to many news sources, North Korea is going to change to
the 8:30 time zone on August 15, one example:
http://www.bbc.com/news/world-asia-33815049

From Paul Eggert (2015-08-15):
Bells rang out midnight (00:00) Friday as part of the celebrations.  See:
Talmadge E. North Korea celebrates new time zone, 'Pyongyang Time'
http://news.yahoo.com/north-korea-celebrates-time-zone-pyongyang-time-164038128.html
There is no common English-language abbreviation for this time zone.
Use KST, as that's what we already use for 1954-1961 in ROK.

From Kang Seonghoon (2018-04-29):
North Korea will revert its time zone from UTC+8:30 (PYT; Pyongyang
Time) back to UTC+9 (KST; Korea Standard Time).

From Seo Sanghyeon (2018-04-30):
Rodong Sinmun 2018-04-30 announced Pyongyang Time transition plan.
https://www.nknews.org/kcna/wp-content/uploads/sites/5/2018/04/rodong-2018-04-30.pdf
... the transition date is 2018-05-05 ...  Citation should be Decree
No. 2232 of April 30, 2018, of the Presidium of the Supreme People's
Assembly, as published in Rodong Sinmun.
From Tim Parenti (2018-04-29):
It appears to be the front page story at the top in the right-most column.

From Paul Eggert (2018-05-04):
The BBC reported that the transition was from 23:30 to 24:00 today.
https://www.bbc.com/news/world-asia-44010705

Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]

Attributed Statements:

Paul Eggert (2016-08-23):

The Korean Wikipedia entry gives the following sources for UT offsets: 1908: Official Journal Article No. 3994 (decree No. 5) 1912: Governor-General of Korea Official Gazette Issue No. 367 (Announcement No. 338) 1954: Presidential Decree No. 876 (1954-03-17) 1961: Law No. 676 (1961-08-07) (Another source "1987: Law No. 3919 (1986-12-31)" was in the 2014-10-30 edition of the Korean Wikipedia entry.) I guessed that time zone abbreviations through 1945 followed the same rules as discussed under Taiwan, with nominal switches from JST to KST when the respective cities were taken over by the Allies after WWII. For Pyongyang, guess no changes from World War II until 2015, as we have no information otherwise.

Steffen Thorsen (2015-08-07):

According to many news sources, North Korea is going to change to the 8:30 time zone on August 15, one example: http://www.bbc.com/news/world-asia-33815049

Paul Eggert (2015-08-15):

Bells rang out midnight (00:00) Friday as part of the celebrations. See: Talmadge E. North Korea celebrates new time zone, 'Pyongyang Time' http://news.yahoo.com/north-korea-celebrates-time-zone-pyongyang-time-164038128.html There is no common English-language abbreviation for this time zone. Use KST, as that's what we already use for 1954-1961 in ROK.

Kang Seonghoon (2018-04-29):

North Korea will revert its time zone from UTC+8:30 (PYT; Pyongyang Time) back to UTC+9 (KST; Korea Standard Time).

Seo Sanghyeon (2018-04-30):

Rodong Sinmun 2018-04-30 announced Pyongyang Time transition plan. https://www.nknews.org/kcna/wp-content/uploads/sites/5/2018/04/rodong-2018-04-30.pdf ... the transition date is 2018-05-05 ... Citation should be Decree No. 2232 of April 30, 2018, of the Presidium of the Supreme People's Assembly, as published in Rodong Sinmun.

Tim Parenti (2018-04-29):

It appears to be the front page story at the top in the right-most column.

Paul Eggert (2018-05-04):

The BBC reported that the transition was from 23:30 to 24:00 today. https://www.bbc.com/news/world-asia-44010705 Zone NAME STDOFF RULES FORMAT [UNTIL]

Years on Record

Methodology Note: The 1970 Rule

tzdb guarantees accuracy for timestamps from 1970 onwards. Transitions prior to 1970 represent best-effort historical reconstructions.