Koliva is prepared for memorial services in the Orthodox Christian Churches. Saturday of the Souls are the Saturdays before Great Lent and Pentecost. Check your calendars for the correct dates, as these are moveable feasts.
How Monks make Koliva on the Holy Mountain
Kollyva - Saturday of Souls
Λεπτομέρια απο κόλλυβα - fiestaperpetua blogspot.com