Thailand followsIndochina Time, which is seven hours ahead ofUTC. The local mean time inBangkok was originally UTC+06:42:04.^[1] Thailand used this local mean time until 1920, when it changed to Indochina Time, UTC+07:00; ICT is used all year round as Thailand never observeddaylight saving time. Thailand shares the same time zone withVietnam,Laos,Christmas Island, &Western Indonesia, as well asparts of Russia.

• Prior to1 January 1901, locations inSiam with anastronomical observatory would adoptlocal mean time based on the observatory's geographic position.Chiang Mai Province and two other provinces each had an observatory, hence, each province had its own distinct local mean time, with minutes of difference between the three locations.
• On 1 April 1920, the mean time of the105th meridian east (passing throughUbon Ratchathani Province) was adopted bySiam as the newstandard time. The mean time of the 105th meridian is 7 hours ahead ofGreenwich Mean Time (i.e., local mean time at theGreenwich Royal Observatory).
• In July 2001, Thailand announced its intention of moving its time forward one hour, to align with bothMalaysia andSingapore and more importantly withWestern Australia,Philippines,Central Indonesia, andTaiwan, i.e.,UTC+08:00.^[2][3] This was met with much criticism and resistance and the plan was withdrawn.^{[citation needed]}

Thailand declared on 16 March 1920 that people would move their clocks ahead by 17 minutes, 56 seconds on 31 March 1920 to match the time in use inSoutheast Asia. The time was switched on 1 April 1920 at 00:00 (old time) to 00:17:56 (new time).^[4]

On1 January 1990, theCabinet of Thailand appointed theRoyal Thai Navy as the official timekeeper for Thailand. Thai Standard Time is derived from fiveatomic clocks maintained by the Royal Thai Navy.

• Six-hour clock used in Thailand
• Thai lunar calendar
• Thai solar calendar

• Time in Thailand
• Geography of Thailand
• Time in Southeast Asia

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