The Beheading of St John the Baptist, a Feast day established by the Church, is also a strict fast day because of the grief of Christians at the violent death of the saint. In some Orthodox cultures pious people will not eat food from a flat plate, use a knife, or eat food that is round in shape on this day. 
August 29 – Feast of St. John the Baptist
The Dormition of The Most Holy Theotokos and Ever-Virgin Mary