Adjusting between standard and daylight savings time

ROE_2015_10_31_0022Richard L. Schmoyer designed the Sunquest sundial to be easily adjusted between standard time and daylight savings time.  Simply loosen the wing-nuts that hold the horizontal and vertical crescents together and slide the aluminum plate to the opposite end of the bracket.

The daylight savings time plate allows for a 1-hour time change without making the delicate longitude adjustments needed for accuracy each time daylight savings time ends or begins.

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Sunquest sundial set for Standard Time, where the time scale arc is near the noon position (adjusted for the longitude to reflect the difference in distance between the sundial’s location and the time zone meridian).

 

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Sunquest sundial set for Daylight Savings Time, with the time scale crescent near the 1’oclock mark (adjusted for the longitude to reflect the difference in distance between the sundial’s location and the time zone meridian).

If your sundial does not have a Daylight Savings Time plate, simply move the time scale crescent 1 hour in the appropriate direction, taking care that the longitude setting is correct.  In the example of the Sunquest sundial at the Mount Cuba astronomical observatory, Daylight Savings Time (DST) and Eastern Standard Time (EST) were permanently stamped into the time scale crescent.

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Eastern Standard Time (EST) and Daylight Savings Time (DST) markings on the Sunquest sundial at the Mount Cuba Astronomical Observatory.