Thai Lunar (Suriyayart)
Sets Vesak and the uposatha days · arithmetic, not observed
The calendar that actually fixes the Buddhist observances — Vesak, Asalha Bucha, Magha Bucha, and the uposatha days that fall on each new and full moon. Twelve numbered months alternate 29 and 30 days, each running fifteen waxing days to the full moon and then waning back to the dark; an intercalary day is added to month 7 in some years, and in others a whole second month 8 (shown here as 8²), which is where Asalha Bucha moves when it appears. It is calculated, not observed: the months open where the Suriyayart arithmetic says they open, which is why an astronomical reckoning of the same calendar can land a day off the date temples actually keep. Note the pair it makes with the Thai Buddhist calendar above — same era, same country, one solar and civil, this one lunar and liturgical.
In UTC at 22:30 on November 2, 2026, this calendar read waning 7 · month 11. The reading above is live, in your own time zone.
At a glance
- Type
- Lunisolar — calculated, not observed
- Origin
- The Suriyayart tradition of Thai astronomy, from the Surya Siddhanta
- Year
- 354 days, or 355 with an extra day, or 384 with an extra month
- Months
- 12 numbered months alternating 29 and 30 days
- Week
- 7 days; the uposatha days follow the moon’s phases
- Leap rule
- An extra day in month 7 in some years; a second month 8 in others
- Counts from
- The Buddhist Era, shared with the civil calendar
- Where it’s used
- Thailand’s Buddhist observances — Visakha Bucha, Asalha Bucha, Magha Bucha
- How it’s worked out here
- The Suriyayart arithmetic itself, which is how Thai almanacs set the observances
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