Ammianus, in a long, because unseasonable, digression (xxvi. 1, and Valesius ad locum), rashly supposes that he understands an astronomical question, of which his readers are ignorant. It is treated with more judgment and propriety by Censorinus (de Die Natali, c. 20), and Macrobius (Saturnal. l. i. c. 12- 16). The appellation of Bissextile, which marks the inauspicious year (Augustin. ad Januarium, Epist. 1l9), is derived from the repetition of the sixth days of the calends of March.