InThailand, two maincalendar systems are used alongside each other: theThai solar calendar, based on theGregorian calendar and used for official and most day-to-day purposes, and theThai lunar calendar (a version of theBuddhist calendar, technically alunisolar calendar), used for traditional events and Buddhist religious practices.

The use of the solar powered calendar was introduced in 1889 byKing Chulalongkorn (Rama V), replacing the lunar calendar in official contexts. The beginning of the year was originally marked as April 1st, however this was changed to January 1st in 1941. The days and months now correspond exactly to the Gregorian calendar. The years follow theBuddhist Era, introduced in 1913 to replace the Rattanakosin Era, which in turn replaced theChula Sakarat in 1889. The reckoning of the Buddhist Era in Thailand is 543 years ahead of the Gregorian calendar (Anno Domini), so the year 2025 AD corresponds to B.E. 2568.

The lunar calendar contains 12 or 13 months in a year, with 15 waxing moon and 14 or 15 waning moon days in a month, amounting to years of 354, 355 or 384 days. The years are usually noted by the animal of theChinese zodiac, although there are several dates used to count the New Year.

As with the rest of the world, the seven-dayweek is used alongside both calendars. The solar calendar now governs most aspects of life in Thailand, and while official state documents invariably follow the Buddhist Era, the Common Era is also used by the private sector. The lunar calendar determines the dates of Buddhist holidays, traditional festivals and astrological practices, and the lunar date is still recorded on birth certificates and printed in most daily newspapers.

• Red numerals markSundays andpublic holidays in Thailand.
• Buddha images markBuddhist Sabbaths,Wan Phra (วันพระ).
• Red tablets with whiteChinese characters mark theNew andFull Moons of theChinese calendar, which typically differ by one day from those of the Thai.
• Thai lunar calendar dates appear below the solar calendar date.

Mundaneastrology figures prominently inThai culture, so modern Thai birth certificates include lunar calendar dates, and the appropriateChinese calendar zodiacal animal year-name for both ThaiHora (โหราศาสตร์, ho-ra-sat) andChinese astrology. Thai birth certificates record the date, month and time of birth, followed by the day of the week, lunar date, and the applicablezodiac animal name. Thai traditionally reckon age by the12-year animal-cycle names, with the twelfth and sixtiethanniversaries being of special significance; but the official calendar determines age at law.

For instance, 12 August 2004 was observed without regard to the lunar date as QueenSirikit's birthday, a public holiday also observed as ThaiMother's Day. Her zodiacal animal is theMonkey and her traditionally significantsixtieth anniversary year was 1992. Born on a Friday, her auspicious birthday colour is blue. Thai auspicious colours of the day are given in thetable of weekdays, followed below it by a link to the Buddha images for each day of the week.

A week (สัปดาห์,sapda or सप्ताह,สัปดาหะ,sapdaha fromSanskrit "seven") is a 7-day period beginning on Sunday and ending Saturday.^[1]

Days of the week are named after the first seven of the nine Indian astrologicalNavagraha; i.e., the sun, moon, and fiveclassical planets.

Note: Colours are those consideredauspicious for the given days of the week, that of Wednesday day being green and of Wednesday night, light green. OfBuddha images representing episodes (ปาง) from his life, there is one that represents a week and others for each day of the week: Monday has three options that are similar and Wednesday, entirely different ones for day and night.^[2]

Thai representations of the planets in deity form are below:

• 
  Phra Athit
• 
  Phra Chan
• 
  Phra Angkhan
• 
  Phra Phut
• 
  Phra Rahu
• 
  Phra Phruehat
• 
  Phra Suk
• 
  Phra Sao

Saturdays and Sundays (Thai:เสาร์-อาทิตย์sao athit) are observed as legal non-workdays (วันหยุดราชการ,wan yut ratchakan) and are generally shown on calendars in red, as are public holidays. Since 1996 and subject to declaration by theCabinet of Thailand, public holidays that fall on weekends are followed by Substitution days (วันชดเชย,wan chot choei) generally shown in a lighter shade of red, as shown above for Monday, 2 August 2004. Buddhistfeasts that are public holidays are calculated according to theThai lunar calendar, so their dates change every year with respect to the solar calendar.Lunar New Year and other feasts observed byThai Chinese vary with respect to both, as these are calculated according to theChinese calendar.

• Date and time notation in Thailand
• Thai solar calendar

• Time in Thailand
• Culture of Thailand
• Calendars

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