Map of Your Local Time vs. True Sun Time |
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Since
the switch to Daylight Saving Time just occurred this weekend, it makes
a good segue into the topic of time zones and shifts in general. The
map shown here was created by Stefano Maggiolo, who has a Ph.D. in geometry
from International School
for Advanced Studies, on his "The
poor man's math blog" web page, and is a Google engineer. His map
depicts by what amount, based on your position in a local time zone,
your clock time differs from the local sun time. Local sun time is relative
to when the sun is due south, at its highest altitude, when noon
(12:00 pm is noon, 12:00 am is midnight)
occurs. Time zones in most of the world are fairly evenly distributed
in 1/24th increments and do make fairly circuitous deviations around
states, provinces and countries, with a very obvious exception in regions
of China. Some of China's time zones span close to 3 hours. Stefano does a great job explaining the orbital mechanics that account for the position of the sun in the sky at noon, and also in providing a little history regarding time zone determinations. The map's key indicates the the redder your locality, the farther behind sun time is, and vice versa for green. That is why the farther west you live, the later the sun sets relative to more easterly points at the same latitude. So, if you like more sunlight in the evening, live westward in your time zone; if you like more light in the morning, live eastward.
There is still the whole issue of Standard Time and Daylight Saving Time switchover. Stefano's map is valid for Standard Time. Daylight Saving Time creates a red shift since everyone is an hour behind the sun time. Where I now live in northern Michigan, sunset around the summer solstice (June 21) is at 9:25 pm, which means it doesn't get truly dark until around 10:30 pm. Sunset was at 9:00 pm in Erie, PA, and at 8:42 pm in Winston-Salem, NC, my former home. I have for a long time been an advocate of banishing the Daylight Saving Time switch and sticking with Standard Time year-round. We just don't need such an artificial time change in our modern world. Here is list on Wikipedia of various countries and regions that do and do not participate in the inanity of Daylight Saving Time. I could make a long list of good reasons to eliminate Daylight Saving Time, but many websites already do that. You can do a Google search, or just read this article from National Geographic titled "Time to Move On? The Case Against Daylight Saving Time."
Posted March 10, 2014
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