Enjoy the blue moon in 2012 Friday night because it won't happen again until 2015, according to a report by the Washington Post.

While the moon doesn't actually turn blue, it's still something of a rare occurrence: the second full moon in a month. Rare enough that some people use the phrase "Once in a blue moon," to indicate something happening very occasionally.

The blue moon event occurs once every 2.7 years, according to the newspaper, and likely won't be noticeable until sometime after 6:30 p.m. on Friday.

Coincidentally, astronaut Neil Armstrong's service also is Friday, according to an Associated Press post on Boston Globe's website.

The next blue moon occurs on July 31, 2015, according to the Washington Post. However, there is expected to be two blue moons in 2018 in both January and March, the Post reported.