Sunday, March 19, 2017

"You Can Say That Again."

I'm revolting. Against daylight-saving time. In a small way.

I have a clock in my Western-decor lair with no numerals on the dial, and a background image on the face that can make it difficult even to see where the hands are in less than full light. So, it being of limited utility anyway I've set it to local sun time -- roughly 48 minutes behind what Eastern Standard Time prescribes, and thus an hour and 48 minutes behind EDT.

Tomorrow being the equinox I think today's reading is as close to the meridian result as human error can achieve for the entire year. Of course, the clock's movement is of less than entirely reliable accuracy.

But I'll worry about that in June.

UPDATE, Monday: I recalculated based on a time-zone width of 15 degrees and the meridian for Eastern Time being 75° West, and found that our solar noon offset should be 39 minutes (1:39 DST) rather than 48, and am adjusting the clock accordingly.

The meridians for other North American time zones are as follows: 60° West for Atlantic (Puerto Rico, Nova Scotia, etc.) 90° West for Central, 105° West for Mountain, 120° West for Pacific, 135° West for Alaska, and so on.

You can determine your longitude using Google Earth, and adjust your Standard Time solar noon offset four minutes per degree, or one minute in time for every 15 minutes (0.25°) of longitude, west or east of your meridian. If you're in the Central time zone and your longitude is 91.25° West, your solar noon will occur at 12:05 p.m. CST, or 1:05 p.m. CDT. Conversely, if your longitude is east of your meridian, say 88° West in the Central time zone, your local solar noon would occur at 11:52 a.m. CST or 12:52 p.m. CDT.

My solar noon doesn't hit at exactly 10:21 a.m. EDT, but I rounded it off to the nearest minute. If the clock I'm keeping at sun time had numerals and hash marks, and an adjustable second hand, I might have made an effort to be more accurate, but what the hey?

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