The Attic calendar is the calendar that was in use in ancient Attica, the ancestral territory of the Athenian polis. This article focuses on the 5th and 4th centuries BC, the classical period that produced some of the most significant works of ancient Greek literature. Because of the relative wealth of evidence from Athens it is the best understood of all the Hellenic calendars. Viewed from the standpoint of the modern Gregorian calendar, this ancient system has many peculiar features. This is a part of its appeal: as a cultural artifact, it opens a window to the mentality of its users.