• Prior to
1 January 1901, locations in
Siam with an
astronomical observatory would adopt
local 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 the
105th meridian east (passing through
Ubon Ratchathani Province) was adopted by
Siam as the new
standard time. The mean time of the 105th meridian is 7 hours ahead of
Greenwich Mean Time (i.e., local mean time at the
Greenwich Royal Observatory). • In July 2001, Thailand announced its intention of moving its time forward one hour, to align with both
Malaysia and
Singapore and more importantly with
Western Australia,
Philippines,
Central Indonesia, and
Taiwan, i.e.,
UTC+08:00. This was met with much criticism and resistance and the plan was withdrawn. == Standardisation of time in Thailand ==