Why is St. Luke's feast day October 18?

St. Luke's feast day is celebrated on October 18 in the Western Christian tradition to honor his contributions as an evangelist and author of the Gospel of Luke and the Acts of the Apostles. This date was established in the early Christian calendar and is observed to commemorate his life and missionary work. St. Luke is also recognized as a patron saint of various professions, including physicians and artists, reflecting his background as a physician and his emphasis on healing in his writings.