The Buddhist calendar is used in mainland Southeast Asia in the countries of Cambodia, Laos, Thailand, Burma, and Sri Lanka in several similar forms. BE stands for Buddhist Era. It was introduced by King Rama 5 in 1889 and is the same as the Gregorian calendar with 12 months and seven days per week. New Year's day was originally on April 6, which corresponded to the founding of Bangkok (April 6, 1782).

In Thailand, Laos, and Cambodia, however, the BE year is calculated slightly differently than in Myanmar, Sri Lanka, and India. The former (Thailand, etc.) consider year 1 to be the year after the Buddha’s death, whereas the later (Myanmar, etc.) consider year 1 to be the year of the Buddha’s passing. Therefore, Thailand is one year behind Myanmar.

In 1912, New Year's Day was shifted to April 1 by King Rama 6. In 1941, Prime Minister Phibunsongkhram decided to adjust the calendar so that the official government year began on January 1, as it does today.