One of the most frequently asked questions of new clock owners is 'What is the purpose of the moon dial and what do the picture or symbols stand for"? The question itself tells us just how far our world has advanced.
Today it is difficult for us to realize just how important the ever-changing phases of the moon were in times gone by. In the late 17th century, the moon dial was added to most tall case clocks so people could plan ahead for when the moon was full and travel at night was not so hazardous. Clock masters endeavored to simulate and approximate the appearance of the moon in the heavens, on the face of clocks.
The arched dial was first used in clocks in the beginning of the 18th century and presented a real challenge to the makers of fine clocks. In approximately 1720, moving figures which moved back and forth with the swing of the pendulum. They used prancing deer, rocking ships, and Father Time with his scythe. At the time there was no practical value of this feature on the clock; it was simply a pleasing way of showing motion and life. After motion had been added in the arch above the dial, the next step was to reproduce the progress of the moon from phase to phase. The proverbial Man in the Moon "Man in the Moon" was used on most dials with a landscape and/or seascape on the other half of the circle - symbols of sea - the rocking ship, and of land - the deer.
It was with the use of gearing and a separate dial piece that the movement of the moon phases on the dial was accomplished. What must be remembered when the owner is using the moon dial is to set the time correctly to A.M. or P.M. so that the dial changes at night in stead of during the afternoon. To accomplish this, simply advance the hour hand (stopping at all chime times and allowing the clock to strike through) listen and watch for the moon dial to advance.
When the moon dial advances the clock is set for night and now the time must be advanced accordingly.