January 1st on his name day (the Feast of the Circumcision of Our Lord)
January 30th along with St. Gregory and St. John Chrysostom, on the feast of the Three Hierarchs.
Tradition tells us that St. Basil would hide coins in breads and cakes to give to the poor. This is why we make a cake or bread with a hidden coin on New Year's Day.
Need a recipe for a Vasilopita cake? I have a recipe for one on the Orthodox Christian Network. http://myocn.net/vasilopita/