Tide clock variables have less impact on the tide at the time of the full moon, so this is usually the best time to set a tide clock. If the tide clock is mounted on a moving boat, it will need to be reset more frequently. The best time to set the clock is at the new moon or the full moon, which is also when the clock can most reliably indicate the actual combined tide. A simple tide clock will always be least reliable near the quarter moon. Tide range is the vertical distance between the highest high tide and lowest
Ecclesiastical full moon with the dates of astronomical opposition, referred to a day beginning at midnight at 0 degrees longitude, to within a day or so. However, the astronomical opposition happens at a single moment for the entire Earth: The hour and day at which the opposition is measured as having taken place will vary with longitude. In the ecclesiastical calendar, the 14th day of the lunar month, reckoned in local time, is considered the day of the full moon at each longitude. Schematic lunar calendars can and do get out of step with the moon. A useful way of checking their performance