The Diasia is a festival in honor of Zeus Meilikhios. Meilikhios or "Easily Entreated" is the title for Zeus in His underworld aspect. Each year in Ancient Athens, sacrifices were made to placate Him so that a good harvest could be had. On this day we honor Zeus by offering Him cakes in the shape of bulls and snakes (Zeus' sacred animals).
In modern times, animal crackers are offered to Zeus, asking that He be kind to us through the rest of the winter and to relieve us of any guilt we have acquired. Following this is a theoxenia for Zeus where worshippers share in His fellowship. It is also customary on this date to give gifts to children as Zeus Meilikhios is considered to be the protector of children. At HTAZP, this has traditionally included activities such as a teddy bear drive for the local children's hospital or Project Smile.
Another element of this festival is the making of kathiskos or ktesios jars to be used in the home for protection of stored foods from spoilage. How often these are emptied and the contents changed varies from one household to the next, but creating and dedicating a new jar for usage throughout the year is often done at this time.