Christian vacations are celebrated adhering to both the Gregorian Calendar and Julian Calendar. Armenian Apostolic Christians rejoice Christmas on six January, as they stick to the Julian Calendar. Greek Orthodox (with the exception of Easter), Catholics, Protestants, and Melkite Christians abide by the Gregorian Calendar and hence rejoice Christmas on 25 December. A Companion to the Ancient Greek Language, write-up by Roger D. Woodward (ed.