Once in a blue moon

My cousin lives in the States so I only see him once in a blue moon.

A: Do you like brandy? B: Once in a blue moon I'll have one.

I don't know why I bought this shirt. It was so expensive and I just wear it once in a blue moon.

What does this idiomatic expression mean?

Answer: rarely, not very often

What is a blue moon?

I discovered the answer just this week. While on holiday around Cádiz, I'd look up into the sky each night and wonder at all the stars (you never really see them when you are stuck in Madrid). I noticed then how rapidly the moon was changing into its full form. Not only that; to me the progress of change didn't seem uniform. So I reached for the ipad to learn something about that white light in the sky.

I didn't find out if or why the pace of change isn't uniform but I read the news about the blue moon.

A blue moon is the second full moon of a calendar month. If you look up at the sky tonight, you will see one. The first full moon was on 1st Aug and today is the second one.

This doesn't happen that often; just every 2 to 3 years.

A full moon occurs every 29.5 days so every month typically has one (though February sometimes doesn't).

Don't expect to see a blue-coloured moon. A blue moon is a full moon like any other.

That's not to say that the moon can't appear to be blue. This phenomenon happens when there is huge volcanic eruption or major forest fire. Certain-sized particles of ash or smoke give the moon its blue colour.

The original definition of a blue moon is "the third full moon in a season (spring, summer, autumn, winter) of four full moons. Using this definition, the next blue moon won't be until 21 August next year.

The expression "once in a blue moon" is much older than the current definition of a "blue moon". So the origins of the idiom likely comes from the much rarer and more literal phenomenon.

Happy moon gazing!

Source: Zelda Selveira (You Tube) Key words: blue moon

Blue Moon

Blue moon
You saw me standing alone
Without a dream in my heart
Without a love on my own

Blue moon
You knew just what I was there for
You heard me saying a prayer for
Someone I really could care for

And then there suddenly appeared before me
The only one my arms will ever hold
I heard somebody whisper, "Please adore me"
And when I looked the moon had turned to gold