moondial

right|thumb|Moondial at Queens' College, Cambridge, showing the table of corrections for the phase of the moon

Moondials are time pieces similar to sundials, using the moon to cast shadows on a marked dial. The most basic moondial is accurate only on the night of the full moon. Every night after that, it loses on average 48 minutes, while every night preceding the full moon it gains 48 minutes. Thus, one week to either side of the full moon, the moondial will read 5 hours and 36 minutes before or after the correct time.