The dark days of Winter

I think I was close to 50 before I heard that the latest sunrise and earliest sunset are NOT on the winter solstice, nor the earliest sunrise and latest sunset on the summer solstice (at least, north of the equator). Blew my mind, especially to think I failed to notice in 50+ cycles. Here’s an explanation to pass a long night.

The Dark Days of Winter — Naval Oceanography Portal

The period between the first week in December and the first week in January could well be called the "dark days" for the mid-northern latitudes. At latitude 40 degrees north, earliest sunset occurs around 8 December each year, and latest sunrise occurs around 5 January. The day with the least amount of daylight is the winter solstice, the first day of winter, around 21 December. Why are not all these dates the same? The answer is not simple. There are two effects which, together, determine the local time of Sun phenomena, such as sunrise, sunset, and transit. One is called the Equation of Time; the other is the Sun’s declination. [keep reading…]

The Dark Days of Winter — Naval Oceanography Portal

But then, it was at least 40 years before I realized the swing between summer and winter solstices is 47 degrees.


About mjh

Mark Justice Hinton lives in New Mexico and loves the Four Corners region, as well as the Rocky Mountains. Write him at
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