Thai CalendarSolar Authority · Lunar Spirit
Thailand runs on the Thai Solar Buddhist Era calendar for law, school, banking, and business—while preserving a lunar rhythm for Buddhism, festivals, and astrology.
Why two calendars?
One country, two complementary ways of keeping time.
Modern Thai calendars often show both: the Buddhist Era year beside the Common Era year, with lunar month and day appearing around Buddhist observances.
Official · สุริยคติ
Thai Solar CalendarSuriyakhati
The Gregorian framework with Buddhist Era year numbering. Leap years follow the same rules as the Gregorian calendar.
- Used for: documents, banking, schools, law, and business
- New Year: January 1 since 1941
- Cultural New Year: Songkran remains April 13–15
Ceremonial · จันทรคติ
Thai Lunar CalendarChanthrakhati
A moon-phase system preserved for Buddhist practice, movable festivals, and traditional astrology.
- Months: alternate between 29 and 30 days
- Adjustment: some years add a day or a month
- Anchors: Wan Phra and major religious observances
Thai Lunar Calendar
The ceremonial calendar stays aligned with the seasons.
The lunar months cannot match the solar year without adjustment. Official astronomical rules determine when an extra day or extra month is inserted so religious observances remain properly aligned.
Timeline of reform
From a lunar court calendar to modern dual time.
In Ayutthaya, the lunar calendar dominates royal and religious life.
Early Rattanakosin encounters growing Western calendar influence.
The Thai Solar calendar is introduced while B.E. numbering is retained.
New Year moves to January 1; 2483 B.E. lasts only nine months.
Solar time governs civil life; lunar time shapes spiritual observance.
Major festivals
Some dates hold steady. Others move with the moon.
Songkran
April 13–15. Thailand’s traditional New Year celebration.
Visakha Bucha
Observed on the full moon associated with May.
Asalha Puja
A July full-moon observance followed by the start of Khao Phansa.
Loy Krathong
Held on the full moon of the twelfth lunar month.
Practical guide
Which calendar should you use?
Use Thai Solar B.E.
Official documents, schools, banks, contracts, and daily administration use solar dates and Buddhist Era years.
Follow lunar observance
Temples, Wan Phra days, and many traditional festivals follow lunar phases and lunar month dates.
Add or subtract 543
For modern dates, add 543 to C.E. for B.E.; subtract 543 from B.E. for C.E.
Which calendar is official in Thailand?
The Thai Solar calendar using Buddhist Era year numbering.
Why do some Thai festival dates move?
They are scheduled by lunar phases rather than fixed Gregorian dates.
Is B.E. always C.E. + 543?
Yes in modern use, with historical context needed around the 1940–41 calendar reform.
Continue exploring
Turn calendar knowledge into practical use.
Solar authority · lunar spirit