The armillary sundial at Oakland Cemetery tells “solar time.” The speed and elliptical shape of the earth’s orbit of the sun, as well as the earth’s tilted axis, mean that the time that is shown on the sundial and “clock time” are not the same.
Use the following chart, plotted specifically for Oakland Cemetery, to see how many minutes should be added to the sundial reading to obtain Eastern Standard Time. Add an additional hour during Daylight Savings Time.
Graph courtesy of North American Sundial Society (NASS)