Two Calendars at Once, Civil and Religious

Each Theravada country that keeps this calendar has layered it differently onto modern civil life rather than replacing it outright. Thailand adopted the Gregorian calendar for civil administration in stages between 1888 and 1941 while retaining Buddhist Era numbering, so Thai official documents, newspapers and currency dates are still given in BE years even though the months and days follow the Gregorian civil calendar underneath; Myanmar, by contrast, has kept a more traditionally lunisolar civil calendar in wider everyday use alongside Buddhist Era numbering.

What the calendar continues to set, in every one of these countries, is the religious year. Vesak, marking the Buddha's birth, enlightenment and death together on the full moon of the sixth lunar month, is the most widely observed Buddhist holiday across the region; Asalha Puja marks the Buddha's first sermon on an earlier full moon and opens Vassa, the three lunar month rains retreat during which monks traditionally remain within a single monastery. None of this is historical description of a calendar once used and now retired. The lunar dates are recalculated and republished every year, and Buddhist Era numbering appears on official documents across Theravada Southeast Asia today exactly as it has for generations.