Days Getting Shorter, but the Sun Sets Later?

December 4, 2010; 9:30 AM ET
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The winter solstice, which occurs on Dec. 21 or 22 each year in the Northern Hemisphere, is the first astronomical day of winter and also the shortest day of the year. However, that doesn't mean it gets dark out the earliest on the winter solstice.

In fact, starting next week, the sun will start setting later and later across most of the contiguous U.S.

You may wonder how days can still be getting shorter through the winter solstice, which occurs on Dec. 21 this year, if the sun is starting to set later in the day.

That is because the sun also rises later in the mornings through the winter solstice, and the rate at which sunrise times are becoming later is higher than the rate at which sunset times are becoming later.

Taking a look at's hometown of State College, Pa., for example, the time of sunrise gets pushed back 13 minutes from 7:19 a.m. on Dec. 1 to 7:32 a.m. on Dec 21. The time of sunset, however, only changes by 3 minutes, going from 4:44 p.m. on Dec. 1 to 4:47 p.m. on Dec. 21.

After the winter solstice, the opposite occurs with the rate at which sunset times become later in the day being higher than the rate at which the sunrise time becomes later in the day. As a result, the days become longer.

During the middle or late part of January, depending on your latitude, the sun will start rising earlier in the mornings, allowing the days to become even longer.

The winter solstice happens when the Earth's axis is tilted the farthest away from the sun. This year, that will occur at 6:38 p.m. EST on Dec. 21.


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