Q. The moon has been up to some unusual behavior recently, prompting question from several readers, including J.B in Groton, and C.C., who didn't provide a hometown.

February last lacked a full moon in 1961; it won't again until 2018.

December's full moon fell on the first day of winter; that last occurred in 1980, and it will happen again this year.

The moon takes an average of 29 1/2 days to orbit the Earth. But the lengths of our months -- 28 to 31 days -- don't precisely match the moon's cycle. So each phase of the moon occurs 12.3683 times per year. That's why over the years oddities like this one occur.

The instant the moon passes the sun it's known as the astronomical new moon. If the moon passes directly in front of the sun it causes a solar eclipse, but usually it passes just above or below and rises and sets almost at the same time, abandoning the night sky

A week later, we see half a moon, what astronomers call the first quarter. One week later, with the sun and moon on opposite sides of Earth, the whole moon is glowing and is on view most of the night. That's the full moon. The last quarter moon occurs a week later. The tiny crescent moon phase occurs a day or two on each side of the new moon.