Both a blue moon and a lunar eclipse occur.

A blue moon refers either to the presence of a second full moon in a calendar month, to the third full moon in a season containing four, or to a moon that appears blue due to atmospheric effects.

A partial lunar eclipse occurred at the Moon’s descending node of orbit on Thursday, December 31, 2009, with an umbral magnitude of 0.0779. A lunar eclipse occurs when the Moon moves into the Earth's shadow, causing the Moon to be darkened. A partial lunar eclipse occurs when one part of the Moon is in the Earth's umbra, while the other part is in the Earth's penumbra. Unlike a solar eclipse, which can only be viewed from a relatively small area of the world, a lunar eclipse may be viewed from anywhere on the night side of Earth. Occurring only about 20 hours before perigee, the Moon's apparent diameter was larger.