Thailand follows UTC+07:00, which is 7 hours ahead of UTC. The local mean time in Bangkok was originally UTC+06:42:04.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 does not observe daylight saving time. Thailand shares the same time zone with Vietnam, Cambodia, Laos, Christmas Island, and Western Indonesia.
|Period in use||Time offset from GMT||Name of time (unofficial)|
|1 January 1880 - 31 March 1920||UTC+06:42:04||Bangkok Mean Time|
|1 April 1920 – present||UTC+07:00||Indochina Time (ICT)|
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 in Southeast Asia. The time was switched on 1 April 1920 at 00:00 (old time) to 00:17:56 (new time).
On 1 January 1990, the Cabinet of Thailand appointed the Royal Thai Navy as the official timekeeper for Thailand. Thai Standard Time is derived from five atomic clocks maintained by the Royal Thai Navy.
Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory in Greenwich, London, reckoned from midnight. At different times in the past, it has been calculated in different ways, including being calculated from noon; as a consequence, it cannot be used to specify a precise time unless a context is given.
Japan Standard Time is the standard time zone in Japan, 9 hours ahead of UTC. There is no daylight saving time, though its introduction has been debated several times. During World War II, it was often called Tokyo Standard Time.
The Mountain Time Zone of North America keeps time by subtracting seven hours from Coordinated Universal Time (UTC) when standard time (UTC−07:00) is in effect, and by subtracting six hours during daylight saving time (UTC−06:00). The clock time in this zone is based on the mean solar time at the 105th meridian west of the Greenwich Observatory. In the United States, the exact specification for the location of time zones and the dividing lines between zones is set forth in the Code of Federal Regulations at 49 CFR 71.
Indian Standard time (IST) is the time zone observed throughout India, with a time offset of UTC+05:30. India does not observe daylight saving time or other seasonal adjustments. In military and aviation time IST is designated E* ("Echo-Star").
The Alaska Time Zone observes standard time by subtracting nine hours from Coordinated Universal Time (UTC−09:00). During daylight saving time its time offset is eight hours (UTC−08:00). The clock time in this zone is based on mean solar time at the 135th meridian west of the Greenwich Observatory.
Central European Time (CET), used in most parts of Europe and a few North African countries, is a standard time which is 1 hour ahead of Coordinated Universal Time (UTC). The time offset from UTC can be written as UTC+01:00. The same standard time, UTC+01:00, is also known as Middle European Time and under other names like Berlin Time, Warsaw Time, Paris Time or Rome Time.
Time in the United States, by law, is divided into nine standard time zones covering the states, territories and other US possessions, with most of the United States observing daylight saving time (DST) for approximately the spring, summer, and fall months. The time zone boundaries and DST observance are regulated by the Department of Transportation. Official and highly precise timekeeping services (clocks) are provided by two federal agencies: the National Institute of Standards and Technology (NIST) ; and the United States Naval Observatory (USNO). The clocks run by these services are kept synchronized with each other as well as with those of other international timekeeping organizations.
Standard time is the synchronization of clocks within a geographical area or region to a single time standard, rather than using solar time or a locally chosen meridian (longitude) to establish a local mean time standard. Generally, standard time agrees with the local mean time at some meridian that passes through the region, often near the center of the region. Historically, the concept was established during the 19th century to aid weather forecasting and train travel. Applied globally in the 20th century, the geographical areas became extended around evenly spaced meridians into time zones which (usually) centered on them. The standard time set in each time zone has come to be defined in terms of offsets from Universal Time. In regions where daylight saving time is used, that time is defined by another offset, from the standard time in its applicable time zones.
Time in New Zealand is divided by law into two standard time zones. The main islands use New Zealand Standard Time (NZST), 12 hours in advance of Coordinated Universal Time (UTC) / military M (Mike), while the outlying Chatham Islands use Chatham Standard Time (CHAST), 12 hours 45 minutes in advance of UTC / military M^ (Mike-Three).
The Atlantic Time Zone is a geographical region that keeps standard time—called Atlantic Standard Time (AST)—by subtracting four hours from Coordinated Universal Time (UTC), resulting in UTC−04:00. During part of the year, some portions of the zone observe daylight saving time, referred to as Atlantic Daylight Time (ADT), by moving their clocks forward one hour to result in UTC−03:00. The clock time in this zone is based on the mean solar time of the 60th meridian west of the Greenwich Observatory.
Hong Kong Time is the time in Hong Kong, observed at UTC+08:00 all year round. The Hong Kong Observatory is the official timekeeper of the Hong Kong Time.
The Newfoundland Time Zone (NT) is a geographic region that keeps time by subtracting 3 1⁄2 hours from Coordinated Universal Time (UTC) during standard time, resulting in UTC−03:30; or subtracting 2 1⁄2 hours during daylight saving time. The clock time in this zone is based on the mean solar time of the meridian 52 degrees and 30 arcminutes west of the Greenwich Observatory.
Singapore Standard Time (SST), also known as Singapore Time (SGT), is used in Singapore and is 8 hours ahead of UTC (UTC+08:00). Singapore does not currently observe daylight saving time.
South African Standard Time (SAST) is the time zone used by all of South Africa as well as Eswatini and Lesotho. The zone is two hours ahead of UTC (UTC+02:00) and is the same as Central Africa Time. Daylight saving time is not observed in either time zone. Solar noon in this time zone occurs at 30° E in SAST, effectively making Pietermaritzburg at the correct solar noon point, with Johannesburg and Pretoria slightly west at 28° E and Durban slightly east at 31° E. Thus, most of South Africa's population experience true solar noon at approximately 12:00 daily.
The time in China follows a single standard time offset of UTC+08:00, despite China spanning five geographical time zones. The official national standard time is called Beijing Time domestically and China Standard Time (CST) internationally. Daylight saving time has not been observed since 1991.
Malaysian Standard Time or Malaysian Time (MYT) is the standard time used in Malaysia. It is 8 hours ahead of Greenwich Mean Time and Coordinated Universal Time. The local mean time in Kuala Lumpur was originally UTC+06:46:46. Peninsular Malaysia used this local mean time until 1 January 1901, when they changed to Singapore mean time UTC+06:55:25. Between the end of the Second World War and the formation of Malaysia on 16 September 1963, it was known as British Malayan Standard Time, which was UTC+07:30. At 2330 hrs local time of 31 December 1981, people in Peninsular Malaysia adjusted their clocks and watches ahead by 30 minutes to become 00:00 hours local time of 1 January 1982, to match the time in use in East Malaysia, which is UTC+08:00. SGT (Singapore) as follow on the same until now.
Sri Lanka Standard Time (SLST) is the time zone for Sri Lanka. It is 5 hours and 30 minutes ahead of GMT/UTC (UTC+05:30).
Coordinated Universal Time is the primary time standard by which the world regulates clocks and time. It is within about 1 second of mean solar time at 0° longitude, and is not adjusted for daylight saving time. It is effectively a successor to Greenwich Mean Time (GMT).
Ireland uses Irish Standard Time in the summer months and Greenwich Mean Time in the winter period..