In a distant past, there was no precise notion of the day among ordinary Thais living in rural areas. However, as they sustained themselves through agriculture, they were attuned to the rhythm of nature. The arrival of the rainy season, followed by a cool and dry season, was regular and provided a reliable indication of the passage of time. Since the length of day and night remained almost constant throughout the year, one could also tell the moment of the day by looking at the sun’s position. It may be that life has become more complex or that we have lost touch with nature, but Thai people nowadays depend on more than one calendar system to guide them in their day-to-day activities and religious practices.

The Thai solar calendar

The most widely used calendar system in Thailand is the Thai solar calendar. It was adopted during the reign of King Rama V (1868-1910) and is based on the Western calendar. However, the years are counted in Buddhist Era (pāli: putthasakkarat), which begins with the passing of the Buddha Gautama in 543 BCE. To convert from the Common Era to the Buddhist Era, we therefore need to add 543. For example, the current year in BE is 2020+543=2563.

Archaic numbering systems

Though now obsolete or confined to the academia, several counting systems preceded the prevalent use of the Buddhist Era. The chulasakkarat or Small Era (also Burmese Era) was introduced in the 16th century (CE) as a result of Burmese conquest in Siam. It gradually replaced the older Saka Era, but fell out of use in 1889 with the establishment of the Rattanakosin Era. This new system took as reference date the founding of Bangkok as the capital in April 1782. However, in 1912 King Vajiravudh (Rama VI) decided that the numbering of years would now follow the Buddhist Era. Moreover, through decree of PM Phibunsongkhram in 1941, the official start of the Thai year was moved to January 1 in accordance with the Gregorian calendar.

The Thai lunar calendar

While the Thai solar calendar is used for most day-to-day purposes, it is altogether a recent custom. Many traditional festivals and religious events in Thailand continue to be tracked by the Thai lunar calendar (patithin chanthrakhati). This version of the Buddhist calendar is employed alongside the Thai solar calendar and, strictly speaking, a lunisolar calendar. A normal year in the lunar calendar comprises 12 months of 29 or 30 days with a total of 354 days. As a result, the lunar year is shorter than a solar year. To compensate, Thai lunar years may add an extra day to a 29-day-month or repeat a 30-day-month at irregular intervals. This practice, though arbitrary, allows the lunar calendar to keep pace with the seasons, which follow the rhythm of the sun.

Lunar-calendar days don’t have names, but carry numbers from 1 to 14 or 15 and are designated by whether they are increasing (waxing) or decreasing (waning). While the period from new moon to full moon (ข้างขึ้น – khang khuen) is always 15 days long, the period from full moon to new moon (ข้างแรม – khang raem) may span from 14 to 15 days.

Lunar-based events in Thailand

Examples of Thai festivals or holy days that are governed by the lunar calendar include the famous Loy Krathong, which takes place on the full moon of the 12th lunar month, and Makha Bucha on the full moon of the third lunar month, which usually falls in February or March. If you plan to attend these celebrations, remember that the solar date varies from year to year!

Songkran, which marks the beginning of the traditional Thai New Year, used to be computed through a complex formula which is only rivaled by the French formula for calculating one’s income taxes. Nowadays it is fixed at April 13 and therefore linked to the solar calendar.

In addition, Thailand observes many Chinese-specific events, such as Chinese New Year. Their dates are calculated based on the Chinese calendar which is different in respect to both the Thai solar calendar and the Thai lunar calendar. But given the large population of Sino-Thais, it is very common that Thai calendars incorporate important Chinese-lunar-regulated days.

The 12-year cycle of the Chinese zodiac

To make things a bit more complicated, the years accompanying the Thai lunar calendar are usually indicated by the presiding animal of the Chinese zodiac. A full cycle repeats itself every 12 years after the succession of all 12 animals: rat, ox, tiger, rabbit, dragon (or the naga), snake, horse, sheep, monkey, rooster, dog, and the pig.

Normally, Songkran is the traditional day in Thailand that sets off the next animal year. However, for the Thai-Chinese community, the transition to the next Chinese zodiac occurs earlier in the year in accordance with Chinese New Year.


The complexity in expressing a date in Thailand reveals the multitude of influences that Thai culture has received throughout its history. To get an understanding and appreciation of the timing of important events, it is certainly a good idea to become familiar with the different calendar systems.

This article was published in putthasakkarat 2563, year of the Rat (according to the Chinese calendar), on the 2nd day of the waning moon of the 4th lunar month.