From the time of the early Buddhist sangha, monks and nuns would gather at the time of the full and new moon to confess wrongdoing and atone for their actions. There was also a recital of the  Prātimokṣa (rules of monastic discipline) and, for lay people, a chance to follow the same rules as ordained Buddhists for a period of twenty-four hours. In Pali these days were known as Uposatha.

The practice of Uposatha was transmitted to other Buddhist countries and in Japanese Sōtō Zen became Ryaku Fusatsu, which translates as “abbreviated or simple ceremony to continue doing good”. The confessions and avowal parts of the original ceremony remain, but instead of the Prātimokṣa, there is a recommittal to the sixteen precepts of Zen which are taken at Jukai and as part of Shukke Tokudo (home-leaving ordination). We confess our past failings, and seek to do better for the future, all while recognizing our frail human nature, casting all into Emptiness as well. Thus, our atonement is also sometimes said to be our “at-one-ment” too.