Ambarvalia

Ambarvalia was a Roman agricultural fertility rite, involving animal sacrifices and held on 29 May[1] in honor of Ceres, Bacchus[2] and Dea Dia.

[3] However, the exact timing could vary since Ambarvalia was a "fariae conceptivae" - a festival not bound to a fixed date.

The private were solemnized by the masters of families, accompanied by their children and servants, in the villages and farms out of Rome.

The public was celebrated within the city's boundaries, in which twelve fratres arvales walked at the head of a procession of citizens who had lands and vineyards in Rome.

Roman farmers' almanacs (Menologia rustica) describe this only as segetes lustrantur ("crops are purified").