Calibrating your Anno Domini by following the following instructions will ensure that your garden sundial works as designed for your particular latitude. Pick a nice sunny day to do your own calibration.
1. Set the gnomon based on the actual calendar date.*
2. Hang the Anno Domini by its hemp rope and adjust it so that, using the pull of gravity, sunlight will shine directly into and straight through the “gnomon hole” and fall on the inside of the dial. When correctly aligned, a bead of light will be clearly visible in the middle of the inside of the dial, allowing you to tell the time.
3. Compare the reading from the Anno Domini with the time on an accurate clock or watch. (Do this at least twice during the day, once in the morning and once in the evening, recording the readings. More frequent readings during the day will give you an even more accurate picture.)
4. The difference between the sundial reading and the clock or watch fading will give you the precise deviation.**
5. This particular model of the Anno Domini is calibrated for 40 degrees of latitude. The closer you are to 40 degrees latitude, the more accurate your reading will be. If you are close to 40 degrees latitude, your reading should be within +5 or -5 minutes. By measuring and calculating your deviations, you can quickly learn how to get an accurate reading with your garden sundial by making any necessary mathematical adjustments.
* Attached product illustration shows the time on March 15th at 7:00 a.m. in conjunction with the symbol of the sign of Pisces from the Zodiac.
** During Daylight Savings Time, add 1 hour