Rattanakosin Era

The Thai solar calendar, (Thai: ปฏิทินสุริยคติ, rtgs: patithin suriyakhati, "solar calendar"), was adopted by King Chulalongkorn (Rama V) in AD 1888 as the Siamese version of the Gregorian calendar, replacing the Thai lunar calendar as the legal calendar in Thailand (though the latter is still also used, especially for traditional and religious events). Years are now counted in the Buddhist Era (B.E.): พุทธศักราช, พ.ศ., rtgs: Phutthasakkarat) which is 543 years ahead of the Christian/Common Era.

The Siamese generally used two calendars, a sacred and a popular ( in the classical sense). The vulgar or minor era (จุลศักราช, chula sakarat) was thought to have been instituted when the worship of Gautama was first introduced, and corresponds to the traditional Burmese calendar (abbreviated ME or BE, the latter not to be confused with the abbreviation for the Buddhist Era, which is the sacred era.)

King Chulalongkorn decreed a change in vulgar reckoning to the Rattanakosin Era (abbreviated RE) (รัตนโกสินทรศก, Rattanakosin Sok abbreviated ร.ศ. and R.S.) The epoch (reference date) for Year 1 was 6 April 1782 with the accession of Rama I, the foundation of the Chakri Dynasty, and the founding of Bangkok (Rattanakosin) as capital in 106 RE, AD 1888.

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