Korean Standard Time

Time in South Korea is given by Korea Standard Time (KST; (Hangul: 한국 표준시; Hanja: 韓國標準時; RR: Hanguk pyojunsi) or also known to some as Seoul Time (Hangul: ) is 9 hours ahead of UTC (UTC+09:00): i.e., when it is midnight (00:00) UTC, it is 9 am (09:00) Korea Standard Time. South Korea does not observe daylight saving time, but experimented with it during the 1988 Seoul Olympics. Korea Standard Time is the same as Japan Standard Time, Indonesian Eastern Standard Time and Yakutsk Time. North Korea was also on Korea Standard Time, but in August 2015 adopted Pyongyang Standard Time, which is 30 minutes behind.

Before modern clocks were introduced into Korea, Koreans kept time with the help of a sundial during the daylight time and a water clock at night. In 1434, Jang Yeong-sil, a Joseon scientist and astronomer with other scientists, developed Korea's first sundial, Angbu Ilgu (앙부일구/仰釜日晷) and was put into service as standard time-keeper of the kingdom and began the standard time at Hanyang (Seoul) which calculated to UTC+08:28. In 1442, Chiljeongsan, an astronomical calendar system that was created during the reign of King Sejong used Hanyang (Seoul) local time as its standard as it overcame the limitations of previous-made calendars. The Korean Empire adopted a standard time of 8.5 hours ahead of UTC (UTC+08:30) in 1908. In 1912, the Governor-General of Korea changed this from UTC+08:30 to UTC+09:00 to align with Japan Standard Time. In 1954, the South Korean government under President Syngman Rhee reverted the standard time to UTC+08:30. Then in 1961, under the military government of President Park Chung-hee, the standard time was changed back to UTC+09:00 again. In 2009, the Presidential administration of Lee Myung-bak tried to reintroduce daylight saving time but failed. It was because that labor organizations objected to the de facto enlarged working hours. It was true the arguments that Korea, whose prime meridian is actually 127˚30′ east longitude not 135˚ east longitude, has adopted daylight saving time by 30 minutes all the year round.

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Wikipedia