Uposatha

Uposatha - the ceremony of repentance of Buddhist monks , is held on the 1st, 8th, 14th, 28th day of the lunar month. Source?? Usually it is the 8th day of the waning and rising moon or 15th day

  It is used both in Theravada and in all Mahayana schools.  The reading monk reads Patimokkhu (Skt .: pratimoksha), the canonical text found in the Buddhist canon is in Suttavibhanga (the first part of the Vinaya pitaki - “basket of disciplinary code”) listing the transgressions.  The monk who has this or that sin comes out and repents.  Lay people are not allowed at the ceremony.  The ceremony has been known since the days of Buddha and the order of its holding is fixed in the Pali canon.  Sins are divided into those requiring exclusion from the community and not requiring.

Violations of the Vinaya Code are divided into several categories.

It was compiled on the basis of a precedent . That is, when “some kind of incident” occurred, which was subsequently qualified as unacceptable, the Buddha, as a rule, delivered a sermon, and the rule was included in vinaya - the code of moral standards. As an example, we can cite the case when one monk could not bear abstinence, and threw himself from a cliff, wanting to commit suicide. He fell on some man and killed him. Buddha noted that suicide is unacceptable. It has become a precept: the inadmissibility of suicide in Buddhism. (See A. Paribok in Afterword to Milindapanye, p. 433)

The book of Milindapanha adjoining the canon on the Pali recorded the explanation given by the early Buddhists why vinaya is given “according to the precedent principle”, and not all at once. King Menander (Pali: Milinda ) asked the Buddhist arhat Nagasena if the omniscient Buddha was not omniscient - and he could not immediately give the bhikkhus (monks) all the rules of vinaya. Nagasena answered him that if all 227 rules were given “in one sitting”, they would have seemed to the monks very numerous and difficult (see: cit. Cit. P. 385)