Break out the flashlights. When a full lunar eclipse takes place on the shortest day of the year, the planet may just get awfully dark.

The upcoming Dec. 21 full moon -- besides distinguishing itself from the others in 2010 by undergoing a total eclipse -- will also take place on the same date as the solstice (the winter solstice if you live north of the equator, and the summer solstice if you live to the south).

Winter solstice is the shortest day of the year in the Northern Hemisphere and marks the official beginning of winter. The sun is at its lowest in our sky because the North Pole of our tilted planet is pointing away from it.

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prior to 2010, when was the last time that we had a total lunar eclipse occur on the same calendar date as the winter solstice? The answer, incredibly, takes us back nearly four centuries.

On Dec. 21, 1638, the full moon was in total eclipse from 1:12 to 2:47 UT. And the solstice occurred later in the day at 16:05 UT.