Whether it is calling home, cleaning your flat or going for a run – if you do it once in a blue moon then this weekend it is time, writes the Daily Mail.

Blue moon is a term for when there are two full moons in a month, which happens about every two-and-a-half year, and the moon will unfortunately not change colour.

Real blue-coloured moons occur even more seldom. In1883, after the Indonesian volcano Krakatoa erupted, blue moons were seen all over the globe for two years.

Astrophysicist Dr Stephen Hughes told Australian ABC: “In some cases there really are blue moons due to dust particles suspended in the atmosphere, which are just the right size to scatter red and yellow light.”

Roly Sussex, a language professor, told ABC that the idiom dates back to 1528. He said: “At that stage it was referring to the moon being mystical, but they had observed already that you only get two moons once every two years or so.”

Last ‘blue moon’ was in March 2010 and the next one coming will be in July 2015, so after Friday you don’t have to worry about the things you do once in a blue moon for a while.

Blue moon is not only an American beer – it is also a very popular feature in song lyrics. Elvis, who lived healthily once in a blue moon, has sung both ‘Blue moon’ and ‘Blue moon of Kentucky’.

Image via Getty.