INTRODUCTION
Any equatorial dial or other construction that gives equiangular hour lines can easily be converted to a civil time dial simply by rotating the hour and minute graduations by an amount proportional to the Equation of Time and Longitude correction on the day in question. This is commonly done using Pilkington's method.
PILKINGTON'S METHOD
This shows how Pilkington's method works. The outer ring has evenly spaced calendar lines. The rotating inner ring with the hour and minute graduations has a similar scale, but each day is adjusted to the Equation of Time & Longitude Correction by 1/4° per minutes.
BACKGROUND THEORY
Here is the background paper by Gordon Taylor on Equiangular Sundials
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