If you’re a Creedence Clearwater Revival fan, you know it can be trouble when there’s a bad moon rising. So if your timepiece has a moon dial, it’s important for it to be operating correctly. Once you have had your timepiece serviced and the moon dial is in good working order, then how do you keep from having a bad moon rising?
As background, your mood dial is calibrated at 29.5 days. Fifteen days into the cycle is a full moon. Because the average “lunation” is 29.5306, over time, your moon dial will be 1 day too fast after 2 years and 8½ months. So how would you ever remember to adjust the moon dial by 1 day at that unusual interval? There’s good news. Consider this: the moon phase discrepancy equates to about 9 hours per year. So after 3 years of moons rising, the moon dial will be 27 hours ahead of the actual moon phase and you can easily make a one-day correction.
To make this adjustment, locate the moon dial disc, located at the top of the clock dial, and (with clean hands) slowly rotate it in a clockwise direction until you have made the 1-day moon correction. Most moon dial discs have two complete moon cycles. You can just rotate the disc clockwise to the next moon cycle and stop at the appropriate moon phase.
And if all else fails and there’s a bad moon rising, you can always contact your favorite horologist for assistance.