It is customary in Catholic, Anglican, and Orthodox circles to have days of the calendar devoted to commemorating certain saints. For instance, December 6th is the Feast Day of St. Nicholas.
Today, being my birthday, it is the Feast Day of St. Anselm of Canterbury on the Roman and Anglican calendars. Anselm is best known for his theological work, Cur Deus Homo, in which he came up with (or greatly elaborated on) the theory of substitutionary atonement. You can read or listen to more about Anselm here.
In the Orthodox calendar, which usually has a whole bunch of saints the West has never heard about, this is the Feast Day of Hieromartyr Januarius. You can listen about him here.
Not a bad group, I must say.