The sectarians had a solar calendar, with a 364-day year. It was divided into twelwe equal months of thirty days, and at the end of each quarter - i.e. in the third, sixth, ninth, and twelfth months - an extra day was added, giving these months thirty-one days. This calendar was the product of an earlier Jewish tradition, reflected, for example, in the apocryphal Book of Enoch. The solar calendar was not used by the bulk of the Jewish people at that time, and consequently, the Qumran sectarians did not observe the festivals on the same days as the rest of the Jewish population. In the Qumranic system, the festivals always fell on the same day of the week: Passover fell on Wednesday; Shavu'ot (Feast of Weeks) on Sunday; and Yom Kippur (Day of Atonement) on Friday. The scrolls also contain evidence of a lunar calendar of 354 days, with months alternating between twenty-nine and thirty days. It seems that the members of the Qumran community used both calendars simultaneously and developed ways of coordinating them.