A 4th-century jug from Voyskovoe on the Dnieper with rows of marks around its neck.

Boris Rybakov (1908–2001), a Soviet archaeologist whose reconstructions of Slavic paganism remain influential but are often disputed, argued that the marks on such vessels form a farming calendar that marked festivals and the right days for rain magic. It is one of his most famous hypotheses, and many archaeologists doubt it.