An ecclesiastical full moon is the fourteenth day of a lunar month (an ecclesiastical moon) in an ecclesiastical lunar calendar. The ecclesiastical lunar calendar spans the year with lunar months of 30 and 29 days which are intended to approximate the observed phases of the moon. Since a true synodic month has a length that can vary from about 29.27 to 29.83 days, the moment of astronomical opposition tends to be roughly 14.75 days after the previous conjunction of the sun and moon. If the ecclesiastical new moon, the first day of the ecclesiastical lunar month, is formally thought of as beginning one day after conjunction, then a formal average opposition will fall at about noon on the 14th day of the same lunar month. The ecclesiastical full moons of the Gregorian lunar calendar tend to