Look to the sky: It's a blue moon on New Year's Eve

According to the modern definition, the term "blue moon" means the second full moon in a calendar month. This year, the first full moon of the month of December was on the 2nd. The next time that there will be a second full moon exactly on December 31 will be the year 2028.

In addition to the second full moon, there will be a partial lunar eclipse visible from some parts of Europe and Asia (centring on India), also today. The last time this occurred on December 31 was in 1990. But don't be alarmed, there were no global consequences in 1990 as many doomsayers had predicted.

The word "month" comes from the word "moon", and most months have only one full moon. Normally, the 29.5-day phase of the lunar cycle matches up almost perfectly with the 28- to 31-day length of calendar months. This one-to-one correspondence occasionally breaks down and gives the chance for the second full moon to squeeze into a single month. It is like when you get paid every second Friday of the month, there will be some months that you get paid three times not twice.

There is lot of folklore about the full moon, one being that it makes for better parties and high booking rates at mental hospitals. Scientific studies, however, deny any such relationships.

There are at least twelve names for moons at certain times of the year, such as "harvest moon", which sometimes lights up the fields after the autumn equinox, enabling farmers to work longer into the night. Two other relatively well-known moons are the "hunter's moon" and the "snow moon". These are monthly or seasonal moons that are restricted to a particular time of year. A blue moon is different. It is a "moveable feast", as it does not fall at any particular time of the year every year.

The modern usage of the blue moon as the second full moon in a month is relatively new. It first appeared in a 1937 edition of the "Marine Farmer's Almanac" to denote an extra full moon in a given season. In 1946, in the magazine "Sky & Telescope", James Hugh Pruett wrote of how two full moons fall in a single month seven times every 19 years, and he called the second full moon a "blue moon". This interpretation was repeated in 1980 in a radio programme and since then has become a well-established, modern-day definition of the term

But the phrase "blue moon" has been around for more than 400 years, and its meaning has shifted through time.

The first appearance in print of this expression dates back before the year 1528, when Shakespeare, in a small item, "Rede Me and Be Not Wroth", said:

 "Yf they say the mone is blewe

  We must believe that it's true."

During those days of the sixteenth century, when there was no astronomical meaning attached to the term, "once in a blue moon" simply meant "absurd" in the same vein as arguing that black is white.

The second meaning seems to have derived from the first. It was used to denote "never", in that it would be on the "Twelfth of Never" - the date of a future occurrence that would likely never come about.

The third meaning denotes occasions when a moon actually turns blue (like in a blue moon and lavender sun). It happened in 1883 when the Indonesian volcano Krakatoa erupted and its ash and dust turned sunsets green and the moon blue all over the world for almost two years.

In 1927, a late monsoon in India turned the moon blue, and forest fires in Newfoundland in 1951 did the same thing. This gives the new meaning to the term that means "rare", which is the way that it's used today - an event that is fairly infrequent and quite irregular.

The fourth meaning appears in many songs, and it is used to denote "sadness, loneliness and melancholy". The lyrics to "Blue Moon" were written in 1934 by Richard Rodgers and Lorenz Hart and recorded by many subsequent artists such as Tony Bennett, Dizzy Gillespie, Billie Holiday, Dean Martin and Frank Sinatra. The term was also made popular by the rock 'n' roller Elvis Presley in his release of the single of that name in 1956. In it, "blue moon" meant "without a love of one's own". Bob Dylan covered the song in 1970. Strangely, the song has been used as the theme song for English football club Manchester City. There is no evidence that the City fans' song of choice originated from the fact that the club has been in decline since winning the league in 1968.

So for those of you who are going out to celebrate this New Year's eve, take peek at that brilliant celestial body on which human beings made a spectacular landing, as it rises over the skyline; enjoy the extra moonlight, as nearly everyone worldwide will see the same full moon all night long. The only exception will be Antarctica, where there's a midnight sun, and no moon. It only happens once in a blue moon.