An Uposatha (Sanskrit: Upavasatha) day is a Buddhist day of observance, in existence since the Buddha's time (600 BCE), and still being kept today by Buddhist practitioners.[1][2] The Buddha taught that the Uposatha day is for "the cleansing of the defiled mind," resulting in inner calm and joy.[3] On this day, both lay and ordained members of the sangha intensify their practice, deepen their knowledge and express communal commitment through millennia-old acts of lay-monastic reciprocity. On these days, the lay followers make a conscious effort to keep the Five Precepts or (as the tradition suggests) the ten precepts. It is a day for practicing the Buddha's teachings and meditation.
^For a description of the contemporary practice of the Uposatha in Thailand, see Khantipalo (1982a), which is also excerpted in this article below.
Kariyawasam (1995), ch. 3, also underlines the continuity of the ancient uposatha practice in Sri Lanka: "The poya [Sinhala for uposatha] observance, which is as old as Buddhism itself, has been followed by the Sinhala Buddhists up to the present day, even after the Christian calendar came to be used for secular matters. Owing to its significance in the religious life of the local Buddhists, all the full-moon days have been declared public holidays by the government."
^The uposatha day is sometimes likened to the Judeo-Christian notion of the Sabbath. Pali English dictionaries that define "Uposatha" as "Sabbath," are Buddhadatta (2002), p. 63, and PED(Rhys-Davids & Stede,1921-25), p. 151.
For an example of the Uposatha being equated with Sabbath by a modern Buddhist master, see Mahasi (undated), p. 2, where he writes: "For lay people, these rules [of discipline] comprise the eight precepts which Buddhist devotees observe on the Sabbath days (uposatha) and during periods of meditation." Harvey (1990), p. 192, also refers to the uposatha as "sabbath-like."