Thai lunar calendar

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The traditional Thai lunar calendar ( Thai : ปฏิทิน จันทรคติ - Patithin Chantharakhati , from Patithin ( ปฏิทิน ) for "calendar" and Chanthra ( จันทรา ) for "moon", thus roughly "calendar based on the moon") is a lunisolar calendar in Siam (Forerunner of present day Thailand ) was the official calendar until 1888 . However, the Buddhist holidays in Thailand , Laos and Cambodia are still determined today using this “lunar calendar”.

Structure of the calendar

The months

The beginning of the month always falls on the new moon . The months alternate between 29 and 30 days, only the seventh month has a variable length due to a leap day . Every three years the eighth month is doubled as a leap month in order to synchronize the lunar calendar with the solar year .

Each month is divided into two parts, the waxing moon ( ขึ้น = khuen) to the full moon always lasts 15 days, the waning moon ( แรม = raem) the remaining 14 or 15 days until the new moon . The 8th, 15th, 23rd and last day of the month are called Wan Phra and are holy days for Buddhists. The 15th day (full moon) is called Wan Phen , the last day (new moon) is called Wan Dap . All other days are just numbered. (see also weekdays in Thailand )

The months are named by simple numbering, with the first month starting in late November through early December. The northern Thai kingdoms used slightly different numbering - month n in Lan Na was month n-2 in Sukhothai, and n-1 in the Shan kingdom of Keng Tung.

The year

Of the four possible lengths of year due to leap month and leap day, only three actually occur. There is no year with a leap month and a leap day. In detail:

  • Pokkatimat ( ปกติ มา ส ), the normal year with 354 days
  • Athikamat ( อธิกมาส , Sanskrit adhikamasa ), the year with a leap month, 384 days
  • Athikawan ( อธิกวาร , Sanskrit adhikavara ), the year with a leap day, 355 days

The rules for calculating the length of the year come from the Hindu lunisolar calendar . The years with a leap month roughly follow the Meton cycle , but this is not the underlying rule.

The New Year Songkran has found originally on the lunar calendar no fixed date, but spring equinox place, but is then due to the neglect of the precession been set to the 13 to 15 April. Since the turn of the year did not previously take place on a fixed date, it could happen that in Athikamat some days occurred twice a year, in other years some days did not appear at all. The 1st month of the Thai calendar is not to be equated with the beginning of a new year.

Holidays calculated according to the lunar calendar

  • Magha Puja is on the full moon day of the third month (February / March)
  • Visakha Puja is on the full moon day of the sixth month (May / June)
  • Asalha Puja is on the full moon day of the eighth month (July / August), Wan Khao Phansa on the day after (first day of the waning moon of the eighth month)
  • Sat Thai is on the new moon day of the tenth month (September / October)
  • Wan Ok Phansa is on the full moon day of the eleventh month (October), the Kathin ceremony the next day (first day of the waning moon of the eleventh month)
  • Loi Krathong is on the full moon day of the twelfth month (November)

Comparison with other countries

Very similar calendars were used in the neighboring kingdoms of Laos , Cambodia, and Burma . The main difference between the Cambodian and Thai lunar calendars is only the naming of the months - in Cambodia they have names, while in Siam they are only numbered. The traditional Burmese calendar is a little more different - it has the year lengths of 354, 384 and 385 days, so a different switching rule applies.

See also


  • John C. Eade: The calendrical systems of mainland south-east asia . Brill, Leiden 1995, ISBN 90-04-10437-2 .
  • John C. Eade: Southeast Asian Ephemeris: solar and planetary positions AD 638-2000 . (Studies on Southeast Asia; 5). Ithaca, NY, USA 1989. ( Online in Google Book Search; last accessed March 21, 2010)
  • Sylvain Dupertuis: Le calcul du calendrier laotien. In: Péninsule , No. 2/3, 1981, pp. 17-79.