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Reading the calendar
Each square shows the moon as it appears at midday, with the percentage of the disc lit in the corner. The four quarters — new, first quarter, full, last — are labelled on the day they fall, and full moons carry their traditional name.
Those percentages move fast around the quarters and slowly around new and full, which is why a moon can look full for two or three nights running. It is only exactly full for an instant, and that instant is listed here.