Time in North Korea, called Pyongyang Time (Korean: 평양시간; Hanja: 平壤時間 or PYT) or Standard Time of the Democratic People's Republic of Korea (조선민주주의인민공화국 표준시간; 朝鮮民主主義人民共和國標準時間), is since May 2018 equal to Korea Standard Time: 9 hours ahead of UTC (UTC+09:00). Like South Korea, North Korea does not currently observe daylight saving time. Time keeping in North Korea is under the State Commission for Science and Technology.
Before modern clocks were introduced into Korea, Koreans kept time with the help of a sundial during the daytime 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 was calculated to be UTC+08:27:52. 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 8½ hours ahead of UTC (UTC+08:30), which is similar to Pyongyang Standard Time, around the beginning of the 20th century. Some sources claim 1908, others claim 1912 and yet another claims that mean local standard time was used prior to 1908 and that UTC+08:30 was used from 1 April 1908 to 31 December 1911 and again from 21 March 1954 to 9 August 1961. In 1912, the Governor-General of Korea changed the time zone to UTC+09:00 to align with Japan Standard Time.
On 5 August 2015, the North Korean government decided to return to UTC+08:30, effective 15 August 2015, and said the official name would be Pyongyang Time or (PYT). The government of North Korea made this decision as a break from "imperialism"; the time zone change went into effect on the 70th anniversary of the liberation of Korea. The South Korean government officials worried about inconvenience in Inter-Korean exchange and cooperation, including commuting to and from the Kaesong Industrial Region, and further difference of lifestyle between the North and South Korean people.
On 29 April 2018, North Korean leader Kim Jong-un announced his country would be returning to UTC+09:00 to realign its clocks with South Korea. On 30 April 2018, the Supreme People’s Assembly of North Korea issued a decree about changing the time zone in North Korea as a further step in unifying Korea and eliminating differences between the South and North. The time zone change was applied at 23:30 on 4 May 2018 (UTC+08:30).
The IANA time zone database contains one zone for North Korea in the file zone.tab, named Asia/Pyongyang.
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After Japan took over Taiwan in 1895, the new empire was divided into two standard time zones: central and western; .... In 1912, Korea adopted the central time zone as a result of its merger with Japan in 1910.
Prior to April 1, 1908 local mean time was used; for some intervals since then, 8.5 hours after U.T. was used as the time zone (from 1 April 1908 to 31 December 1911 and from 21 March 1954 until 9 August 1961).