Thai solar calendar

Origins and royal reforms

Siam historically relied on both a sacred calendar and a popular lunar calendar linked to Burmese counting. In 1888, King Chulalongkorn, or Rama V, adopted a solar framework to serve as the legal civil calendar. The king initially established the Rattanakosin Era in 1889, counting years from the founding of Bangkok and the Chakri dynasty in 1782. Decades later, King Vajiravudh transitioned the official count to the Buddhist Era, establishing 1 April as the opening of each civil year. In 1940, Prime Minister Phibunsongkhram aligned the start of the year with the international date of 1 January, giving that transitional year only nine months.

Months and naming patterns

Each month receives a name drawn from Hindu astrology and Sanskrit terms for the zodiac. The endings of these names instantly tell a reader how many days the month contains. Months with thirty-one days conclude with the suffix akhom, rooted in a word meaning arrival. Thirty-day months finish with ayon, which shares a similar meaning of arrival. February ends with aphan, derived from a Sanskrit term for being bound or fettered. When a leap year requires an extra day, this leap day is called Athikasurathin, combining ancient words for addition and solar movement.

The Buddhist Era count

The year numbering in Thailand operates on the Buddhist Era, which places its starting point at the passing of Gautama Buddha in 543 BC. Because of this baseline, subtracting 543 from the Thai year produces the Common Era equivalent. This numbering system appears on official government paperwork, street signage, banking documents and newspapers. While practical and widely understood within the country, the large number difference can create historical mix-ups or digital software errors, such as computer applications reading the advanced year as an expired license date.

New year observances

Thailand marks the turn of the year at multiple points on the calendar. The official civic year starts on 1 January, which is observed as a national public holiday. In mid-April, the nation celebrates Songkran, the traditional solar new year that occurs when the sun enters the sign of Aries. Songkran is also a public holiday and marks the transition to the next Chinese zodiac animal in traditional Thai reckoning. Meanwhile, Thai Chinese communities follow their own lunar calendar to determine the exact date of Chinese New Year.

How Thai solar calendar is kept

Thai citizens, businesses and state institutions use the solar calendar for everyday scheduling, administration and record keeping. The calendar year opens on 1 January with modern civic celebrations. Throughout the months, daily life proceeds according to twelve solar months named after zodiac signs. In April, people celebrate Songkran from 13 to 15 April as the traditional new year, marking the zodiac animal transition. Religious festivals continue to be scheduled alongside this system using lunar calculations.

When and where

The solar calendar runs continuously through twelve months, starting on 1 January. The year count increases on New Year's Day. Key holiday dates include 1 January for the civil year and 13 to 15 April for Songkran, the traditional solar new year fixed to the sun's entry into Aries.

This calendar is used across all provinces of Thailand as the official national standard. It is observed in government administration, education, business and daily public life, alongside traditional lunar dates used in local temples.

What Thai solar calendar means

The calendar combines Buddhist spiritual heritage with modern statecraft. Counting years from the passing of Gautama Buddha anchors civic time in Buddhist devotion. At the same time, Sanskrit names based on Hindu astrology link each month to astrological transitions, creating a continuity between ancient cosmology and modern administration.

Days Thai solar calendar is marked

Questions people ask about Thai solar calendar

See also

VesakA day to honor the birth, awakening, and passing of the Buddha, kept by Buddhists across Asia.Loy KrathongA Thai festival of floating leaf baskets on rivers to honor water and release negativity.KathinaA Buddhist season of offering new robes and gifts to monks after the rains retreatRoyal Ploughing CeremonyA royal agricultural rite opening the rice season across mainland Southeast Asia

Good reading and sources

• Thai solar calendar on WikipediaEncyclopedia
• More photos on Wikimedia CommonsPhotos and video
• Wikidata recordOpen data

It may contain mistakes. Traditions differ from one family, village and community to the next, and the people who keep them know them best. If something is wrong, tell us. Last refreshed 2026-10-04.