Why do they say "once in a blue moon?"?

Answer 1

It's a folk saying...it means the second full moon in a month. Fairly rare.

Answer 2

Selah is correct. That saying describes something that does not occur very often. A 'blue moon' is the second full moon in a calendar month, something that only happens now and then. H ADDENDUM: You are getting a lot of confusing answers for a simple question. The simple explanation is that a 'blue moon' is an expression for something that seldom occurs. A blue moon is the second full moon in a calendar month. May 31, 2007 was the date of the last blue moon. The rare phenomenon of two blue moons occurring in the same year happens approximately once every 19 years. 1999 was the last time a blue moon appeared twice and this was during in January and March. I was lucky enough to see both. Of course, anytime the moon just happens to appear 'blue' due to atmospheric condition, that can also be called a "blue moon." In my lifetime I have never seen this happen and I doubt that any poster here has. The 'other' explanation for a blue moon is when there are four full moons during a growing season; the third full moon is called a "blue moon." The last time that happened was in 2005. H

Answer 3

There are in fact two definitions for a blue moon. According to the more recent definition, a blue moon is the second full moon in a calendar month. For a blue moon to occur, the first of the full moons must appear at or near the beginning of the month so that the second will fall within the same month (the average span between two moons is 29.5 days). June 2007 will have two full moons: the first on June 1, the second on June 30—that second full moon is called the blue moon.

The Other Kind of Blue Moon
An older definition for the blue moon is recorded in early issues of the Maine Farmer's Almanac. According to this definition, the blue moon is the third full moon in a season that has four full moons. Why would one want to identify the third full moon in a season of four full moons? The answer is complex, and has to do with the Christian ecclesiastical calendar.

Some years have an extra full moon—thirteen instead of twelve. Since the identity of the moons was important in the ecclesiastical calendar (the Paschal Moon, for example, used to be crucial for determining the date of Easter), a year with a thirteenth moon skewed the calendar, since there were names for only twelve moons. By identifying the extra, thirteenth moon as a blue moon, the ecclesiastical calendar was able to stay on track.

Answer 4

There are in fact two definitions for a blue moon. According to the more recent definition, a blue moon is the second full moon in a calendar month. For a blue moon to occur, the first of the full moons must appear at or near the beginning of the month so that the second will fall within the same month (the average span between two moons is 29.5 days). June 2007 will have two full moons: the first on June 1, the second on June 30—that second full moon is called the blue moon

I hope this helps.

Answer 5

It is because a blue moon does not come very often, A Blue Moon is the 2nd full moon in a month.

Answer 6

A blue moon is when there are two full moons in the same month, which happens only every so many months. That second full moon is called a blue moon. The saying refers to something that happens rarely.

Answer 7

rarely ........

A rising full Moon lights the scene in The Fishing Party, painted by Fitz Hugh Lane after a visit to the coast of Maine in August 1850. That month contained a Fruit Moon, according to the Maine almanac's rules.Recent decades have seen widespread popular embrace of the idea that when a calendar month contains two full Moons, the second one is called a "Blue Moon." The unusual pattern of lunar phases in early 1999 — two full Moons each in January and March, and none at all in February — triggered a groundswell of public interest. Countless newspapers and radio and TV stations ran stories about Blue Moons.
on the net ...............

Answer 8

Once in a Blue Moon
"Blue moon" appears to have been a colloquial expression long before it developed its calendrical senses. According to the Oxford English Dictionary, the first reference to a blue moon comes from a proverb recorded in 1528:

If they say the moon is blue,
We must believe that it is true.

Saying the moon was blue was equivalent to saying the moon was made of green (or cream) cheese; it indicated an obvious absurdity. In the 19th century, the phrase until a blue moon developed, meaning "never." The phrase, once in a blue moon today has come to mean "every now and then" or "rarely"—whether it gained that meaning through association with the lunar event remains uncertain.

Answer 9

A "blue" moon is the second full moon in a month. Since a full moon only happens once every 28 days, it only happens about once a year that you have 2 full moons in one month.

So, "once in a blue moon" means that the thing happens pretty rarely.

Answer 10

Because it hardly ever happens. It is when there are two full moons in the same month.
On average, there will be 41 months that have two Full Moons in every century, so you could say that once in a Blue Moon actually means once every two-and-a-half years

Answer 11

Well there is a astronomical phenomina called "Blue Moon" where the full moon actually appears Blue. But it doesn't happen very often. So if you are trying to say that something happens very rarely, then you can express it by saying it happen's "Once in a Blue Moon" & people will understand just how rare you mean.