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soc.culture.thai Culture FAQ
Section - C.5) Traditional Thai Calendar System

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This writing came out of a need to understand Thai calendar to
explain to a foreigner. I must state that I am not an expert in
this matter but it turns out that many Thais that I asked did not
know much about their own traditional calendar system either. So 
this writing may be more beneficial to a Thai than to a foreigner.

This material is intended only to introduce the traditional Thai
calendar concept to readers. There are many other aspects
of temporal information used in Thai language. Many other time
keeping terms such as "Moang", "Yam", "Toom", "Tee", or short-
term time keeping such as "Yok" (based on coconut water clock)
are not covered here because I am not qualified to discuss them
in linguistics terms.

Please help correct any errors you find, especially in the
spellings of Thai and Pali/Sanskrit words.

Rom Hiranpruk
Department of Computer Science
Faculty of Science, Ramkhamhaeng University
August 1993


Rom Hiranpruk compiled and translated from:

1.   Siam Almanac 2529, Siam Bann Ltd., Bangkok, 1986.
2.   Kloy Songbandhit, One Hundred Year Calendar, Silpabannakarn
     Publishing, 1960.
3.   So Sethaputra, New Model Thai-English Dictionary, So
     Sethaputra Press, 1965.
4.   Royal Academy, Thai Dictionary, Aksorncharoentasana Press,

THAI NAGASATRA (Thai Year Names)

There are twelve Year Names in Thai: Chuad (Rat), Chalu (Bull),
Khal (Tiger), Toa (Hare), Maroang (Big Snake), Maseng (Little
Snake), Mamia (Horse), Mamaae (Goat), Wog (Monkey), Raga
(Rooster), Jau (Dog), Goon (Pig). 

These names cover twelve-year cycle but can be extended to cover
one-hundred-and-twenty-year cycle by adding a counter suffix
after the name: ek (one), to (two), tri (three), jatawa (four),
benja (five), cho (six), satawa (seven), attha (eight), noppa
(nine), samriti (ten). Then add the word Sok (year). For example,
Pi Chuad To Sok is the second Chuad year in the 120-year cycle.


Chantarakati is the way to keep dates by using the Moon's orbital
cycle around the Earth. Each cycle is 29 days, 12 hours, 44
minutes. Chantarakati month is therefore 30 days or 29 days
alternately for the whole year. 

Each month begins on Wan Kuen Nueng Kham (first day of the waxing
moon). Wan Kuen Sib Ha Kham (day of the full moon) is the middle
of the month. Wan Dub is last day of the month which is either
Wan Ram 15 Kham or Wan Ram 14 Kham depending on whether that
month has 30 or 29 days.

Because each month is 30 or 29 days long, the Lunar-year days
will be shorter by about 12 days than the actual time the Earth
circles the Sun. To be synchronous with the seasonal changes,
every two or three years another month is added to Duen Pad (the
Eighth month) and called Duen Pad Lung (the latter Eighth month).
Such year with two Duen Pads is called ATHIKAMAS.

The Chantarakati months are named from one to twelve: ai (one),
yi (two), sam (three), si (four), ha (five), hok (six), jed
(seven), pad (eight), kao (nine), sib (ten), sib-ed (eleven),
sib-song (twelve). The first month on Prokatimas year (ordinary
year) falls in November but in Athikamas year (year with two Duen
Pad's) it falls in December.

Chantarakati date is stated by the moon-position/lunar-month-
name/year-name, for example: Kuen Sib Kham/Duen Sib-ed/Pi Mamia
Cho Sok which is 7th October B.E. 2497. If the day is not
provided, finding the day in this dating system requires a
calendar table.

Furthermore, to compensate for the still missing days, every 4 or
5 years another day is added to Duen Jed (the Seventh Month)
to make it a 30-day month. This added day is called ATHIKAWARA
and cannot occur on Athikamas year.


     The date system based on solar year which is currently the
     international date system based on Gregorian Calendar with
     January 1st as the first day of year. 
     Thailand adopted the solar calendar officially during the
     reign of King Rama V in B.E. 2431 using April 1 as the first
     day of year. In B.E. 2483 the government of Field Marshall
     Pibulsongkram changed the first day of year to January 1,
     therefore B.E. 2431 and B.E. 2483 are shorter than usual.

     Last day of a lunar month which is Wan Ram Sib-ha (15) Kham,
     or Wan Ram Sib-si (14) kham depending on whether that lunar
     month has 30 or 29 days.

     Day of the full moon.

     Buddhist holy day which falls on the 8th, 15th, 23rd, and
     29th or 30th day of the lunar month. 
     This is a day of special observance of the Sela and
     contemplation of Dhamma for Buddhists. Wan Phra occurs 4
     times a month on: Wan Kuen Pad (8) Kham, Wan Kuen Sib-ha
     (15) Kham (Full moon), Wan Ram Pad Kham, and Wan Dub (last
     day of the lunar month). 
     Day that monks shave which is one day before each Wan Phra.

     Day of the full moon and last day of the lunar month (Wan
     Phen and Wan Dub) when monks recite Phra Patimokha and 
     Buddhists laypeople observe Ubosoth Sela (the 8 precepts).

     The day when the sun enters Aries; reckoned according to the
     Old Indian Solar Calendar to fall on April 13 through 15.

     Day of the week named by counting Sunday as 1, Monday as 2,
     and so on.

     The waxing moon; the period from new moon to full moon.

     The waning moon; the period from full moon to new moon.

     Ordinary month, ie. not the extra month (second Duen Pad).
     Year with Prokatimas has just 12 months.

     Ordinary day, ie. not the extra day added to Duen Jed. Year
     with Prokatiwara has 29 days in Duen Jed.

     Ordianary February with 28 days.

     Extra lunar month added as the second Duen Pad to keep lunar
     year in synchrony with the solar year. Lunar year with
     Athikamas has 13 months and occur every 2 or 3 years.

     Extra day added to Duen Jed to compensate for the missing
     hours each year. Lunar year with Athikawara has 30 days in
     Duen Jed and occur every 4 or 5 years (not in Athikamas

     February with 29 days to compensate for the missing hours
     each year in solar year. Year with Athikasuratin (leap year)
     occurs every 4 years, except in the last year of the A.D.
     century that is not divisible by 400, ie. A.D. 2000 would be
     an Athikasuratin year but A.D.2100 is not.

     The year of the passing of Lord Buddha is counted as B.E. 1.
     Therefore the new year is Wan Ram nueng Kham, Duen hok, the
     day AFTER Visakapuja Day. King Rama V changed the new year
     day to April 1 starting after March 31, 2431. Later the new
     year was changed to January 1 starting after December 31,

     The year of the birth of Jesus Christ is counted as A.D. 1.
     (A.D. is B.E. minus 543)

     A solar calendar that began in the victory year in the reign
     of an Indian king in the SAKA dynasty. The new year is the
     day the Sun enter Aries, called Songkran.
     (Mahasakaraj is B.E. minus 621)

     A lunar calendar started by a Burmese king. The new year is
     on Kuen Nueng Kham, Duen Ha. But the year count is still at
     Songkran as in Mahasakaraj.
     (Julasakaraj is B.E. minus 1181)

     A solar calendar decreed by King Rama V, counting the first
     year of establishing Bangkok as the Capital as R.S. 1. April
     1, is the new year day starting after March 31, 2431. This
     calendar was abolished by King Rama VI.
     (Ratanakosinsok is B.E. minus 2324)

     A solar year is 365 days, 5 hours, 48 minutes, and 45.68
     seconds. This is the time it takes for the Earth to circle
     the Sun. This calendar system keeps the season in step with
     the months. There are two major western calendar developments.


     Julius Caesar improved the older lunar calendar which has
     gone three months out of step with the actual season. Julius
     Caesar decreed a year with 365 days and every 4 years a day
     is added to February to make it 30 days. This system began
     in B.E. 497. The new year is on January 1. Each month has
     alternately 31 and 30 days except February with 29 days.

     Roman Emperor Augustus further adapted the Egyptian lunar
     calendar to the Julian calendar and reduce February to 28
     days. The removed day is added to the month now called
     "August" to make it 31 days instead of 30 days.

     Although Julian calendar is practical, it is not accurate
     enough with 365.2 days a year. The errors will accumulate to
     about 1 day every 128 years.


     In B.E. 2125, Pope Gregory 33rd of Rome improved upon the
     Julian calendar the rule to provide for leap year every four
     years except at the of the century A.D. that is not
     divisible by 400. This means that A.D. such as 1600, and
     2000 are leap years where 1700 and 2100 is not.

     This system is a lot more accurate with each year averaging
     365 days, 5 hours, 49 minutes, and 12 seconds which is only
     about 23 seconds off per year. It takes 3,323 years to be
     off by 1 day.

     Gregorian calendar was used from October 5, B.E. 2125
     onward. The date was compensated for past errors to be
     October 15, B.E. 2125. It is the current internationally
     accepted calendar system.

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