 By the late 2nd century AD, extant calendars no longer show these letters, probably as a result of calendar reforms undertaken by Marcus Aurelius that recognized the changed religious environment of the empire.On surviving Roman calendars, festivals that appear in large capital letters (such as the Lupercalia and Parilia) are thought to have been the most ancient holidays, becoming part of the calendar before 509 BC.Some of the oldest festivals are not named for deities.