Ascension Day, a festival of the Roman Catholic and Episcopal churches, kept in commemoration of the ascension of Jesus, recorded by the evangelist to have happened on the 40th day after his resurrection. It is kept on Thursday, and the day is also called Holy Thursday. It has been observed at least since A. D. 68. In the 5th century Mamertus, bishop of Vienne, instituted a three days' preparation for this festival. This occupies the three days immediately preceding Holy Thursday, which are called rogation days.