The Lunar Calendar and Some other Aspects of Thai Time

For beginners, the lunar calendar can be quite difficult to understand, but it is important to us here because it is used to determine religious events and observations. The lunar calendar is based on the phases of the moon. Each complete cycle is 29 days, 12 hours and 44 minutes long, which is the time it takes for the moon to complete its orbit around the Earth. Each month begins on the first day of the waxing moon (wan khun 1 kham) and continues until the middle of the month — the full moon — which occurs on the fifteenth day (wan khun 15 kham). The waning moon is then counted from 1 to 15 beginning with ram 1 kham, until the new moon is reached.

Alternate months have either 29 or 30 days, so the last day (wan dap) is either called wan ram 15 kham or wan ram 14 kham. In order to keep it synchronized with the seasons, an extra month is added every two or three years. Wan phra are special holy days that fall on the 8th, 15th, 23rd, and 29th or 30th day of the lunar month.

wan phra or wan ubosot (uposatha): Buddhist holy days that fall on the 8th, 15th, 23rd, and 29th or 30th day of the lunar month (that is, wan khun 8 kham, wan khun 15 kham (full moon), wan ram 8 kham, and wan dap (the last day of the lunar month). These are days of special observance of the precepts and contemplation of the Dhamma. Buddhist laypeople observe the 8 precepts (3 more than normal — see Aspect dealing with the Precepts). Also, on the days of the full moon and last day of the lunar month (wan phen and wan dap), monks recite the Patimokkha (227 Rules of the Order).

wan kon: the day that monks (may) shave their heads, which falls on the day before wan phra. A day of merit making.

The Year of the Rat Pi Chuat
The Year of the Ox (Bull) Pi Chalu
The Year of the Tiger Pi Khan
The Year of the Rabbit (Hare) Pi Tho
The Year of the Dragon (Big Snake) Pi Marong
The Year of the Snake Pi Maseng
The Year of the Horse Pi Mamia
The Year of the Goat

Pi Mamae

The Year of the Monkey Pi Wok
The Year of the Rooster (Cock) Pi Raka
The Year of the Dog Pi Cho
The Year of the Pig Pi Kun


Buddhist Era (B.E.): The official year in Thailand is counted from the death of the Buddha. The year the Buddha passed away is 0 B.E. To convert from A.D. to B.E., one can generally add 543. For example, the year 2000 A.D. would be 2543 B.E. in Thailand. Although the Buddhist Era dates are widely used, most people are aware of the Gregorian dates. In neighboring India, Sri Lanka, and Burma the date of the Buddha’s passing is counted as 1 B.E., however in Thailand, Laos, and Cambodia it is counted as 0 B.E.

Thai people also analyze character according to the day on which you were born. Visit Paisarn’s sanuk website.

The following sites have an abundance of information on this subject:

Uposatha Days

The Eight Precepts for Uposatha

Textual Explanation of Thai Lunar Calendar

An excellent cultural-linguistic study of Thai Time by Anthony Diller

To dig even deeper see:

J. C. Eade, Southeast Asian Ephemeris: Solar and Planetary Positions, A.D. 638-2000. Ithaca: Cornell University Southeast Asia Program, 1989.

The author checked the dates of more than 250 inscriptions from Burma, Thailand, Cambodia, and Laos with a high degree of accuracy and reproduced old calendrists' calculations in an established calendar for each year from A.D. 638 to 2000. The introduction provides an outline of the calendrical system and some explanation of its technical aspects. This work is of extreme usefulness to all scholars of Southeast Asia when verifying or discounting calendrical and astronomical records in royal and monastic inscriptions, as well as when resolving ambiguities and correcting misreadings.