Blue Moons & Black Moons – 2018 (Simone Matthews)

moonWe often use the term ‘once in a blue moon’ to describe a situation or event that is rare. But where did this saying come from?

We metaphorically use this expression of BLUE MOON as it relates to one of the following lunar events:

1. A month in which there are two Full Moons.   A calendar month usually has one Full Moon,  but where a 2nd Full Moon occurs within the month this is called a BLUE MOON.  This is the most popular definition of a BLUE MOON.

2. The 3rd Full Moon in a season of 4 Full Moons.  There are usually 3 Full Moons within a season, but where a season contains 4 Full Moons, the 3rd of 4 Full Moons is called a BLUE MOON.   Note that a season is defined as the time period between a solstice and equinox or equinox and solstice.

Whilst the term ‘once in a blue moon’ doesn’t really relate to the colour of the moon, the moon can take on a blueish appearance at times due to changes in atmospheric conditions such as smoky haze or dust particles.

BLUE MOON – 2nd Full Moon in Calendar Month

How did the 2nd Full Moon in a Calendar Month come to be called a BLUE MOON ?
The March 1946 edition of  Sky and Telescope magazine, contained an article by James Hugh Pruett entitled “Once in a Blue Moon”.  In this article where he inadvertently misinterpreted/simplified the 1937 Maine Farmers Almanac definition of BLUE MOON:  “Seven times in 19 years there were – and still are – 13 full moons in a year. This gives 11 months with one full moon each and one with two. This second in a month, so I interpret it, was called Blue Moon.”   As a side note here, interestingly 1937 only had 12 full moons!

EarthSky’s Deborah Byrd happened upon a copy of this old 1946 issue of Sky and Telescope in the stacks of the Peridier Library at the University of Texas Astronomy Department in the late 1970s. Afterward, she began using the term Blue Moon to describe the second full moon in a calendar month on the radio. Later, this definition of Blue Moon was also popularized by a book for children by Margot McLoon-Basta and Alice Sigel, called “Kids’ World Almanac of Records and Facts,” published in New York by World Almanac Publications, in 1985. The second-full-moon-in-a-month definition was also used in the board game Trivial Pursuit.

Thus whilst this definition of BLUE MOON is not technically correct, it is the most popular definition and most commonly used.

sister moon circlesBLUE MOON – 3rd of 4 Full Moons in a Season

The Maine Farmer’s Almanac defined a Blue Moon as an extra full moon that occurred in a season (and their definition of season related to winter, spring, fall, summer).  A season normally has 3 full moons, however if there are 4 full moons in a season then the third full moon is called the BLUE MOON and the 4th moon is referred to as the last of that season.

Energy of Blue Moons

The Full Moon is a powerful time of gratitude, gracefully acknowledging the beauty of life itself and all you have brought into beingness.  It is also a profound opportunity to let go of any aspects of your life that no longer serve the grandest vision of your Soul.

Sooo… during a BLUE moon we have DOUBLE the chance to do just that.  The energy of a Blue Moon we will be dependent upon the what sign the Moon is transiting at the time and the influence of other celestial transits too.


Also, it is rare for two Blue Moons to happen in any one year… however in 2018 we have 2x Blue Moons !  These double Blue Moons only happen about 3 to 5 times every 100 years!

Here is a list of upcoming 2nd Full Moon in a Calendar month Blue Moons

  • 31 January 2018
  • 31 March 2018
  • 31 October 2020
  • 31 August 2023

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