As a rule, whenever St. Peter has a feast day, St. Paul is, likewise, commemorated.  Next week we will celebrate the Conversion of St. Paul on January 25.  On that day we will also commemorate St. Peter.  Later in the year, on June 29, we will again remember these two apostles with the Feast of the Saints Peter and Paul.  Just as they were joined in life in the heroic work of our Lord, joined in receiving the crown of martyrdom on the same day, and joined in honor in heaven, it is tradition that the two Founders of the Roman Church can never be divide.

Taken From: Butler’s Lives of the Saints