Dziady was an ancient Slavic feast (celebrated mainly by Belarusians, Ukrainians and Poles) to commemorate the dead. Literally, the word is translated as “Grandfathers”. It was held twice every year (in the spring and autumn). During the feast the ancient Slavs organized libations and ritual meals. In local mythologies such feasts were organized both for the living and for the souls of the forefathers who joined the dziady after dark.
In the most original form of the rite Slavs used to leave honey, groat and eggs for the wandering souls. They also used to make bonfires, which were believed to show the spirits of the dead the way to their homes, so they could spend the night with their families (we can see the echo of this custom in modern grave lanterns, which are a common tradition in Poland, especially during the All Saints’ Day). However, the fire was also believed to prevent upyrs from coming to our World.
In Poland, the tradition prevailed in the form of Christian Zaduszki feast. In Belarus, Dziady (Дзяды) were usually held on the last Saturday before St. Dmitry’s day, end of October/beginning of November (Dźmitreuskija dziady, St.Dmitry’s Dziady). There were also ‘Trinity Day Dziady, 'Shrovetide Dziady, and some other dates.
Lithuanians also have similar feast day, called Ilgės. It has roots in pagan times, and differs slightly from the Slavic Dziady.