August 2012 counts as extra special because two full moons take place within the bounds of a single calendar month. Most of the time, a calendar month only features one full moon. But in cycles of nineteen years, or 228 calendar months, seven to eight calendar months harbor two full moons.
Day and night sides of earth at instant of first August full moon
For the mainland United States, the first full moon of August falls tonight (Wednesday, August 1) at 11:27 p.m. EDT, 10:27 p.m. CDT, 9:27 p.m. MDT or 8:27 p.m. PDT. By Universal Time – the standard clock time at the prime meridian of Greenwich, England – the moon turns full on Thursday, August 2, at 3:27 in the morning. Although the full moon occurs at the same instant worldwide, the clock reads differently according to time zone.
The second full moon of August 2012 comes on August 31, at 13:58 Universal Time. By popular acclaim, the second of two full moons to fall in the same calendar month goes by the moniker of blue moon. Although there are other definitions for blue moon, this is probably what most people think of when the term is being used.
If we exclude February, the month is either 30 or 31 days long. On the other hand, the time period between full moons varies from about 29.3 to 29.8 days. So if the full moon comes very early in the month – like it does in August 2012 – that leaves enough time for another full moon to beat out the clock before the month’s end.
February is the only month that doesn’t have enough room for two full moons, and it’s the only month where it’s possible to have no full moon at all. In years where February has no full moon – such as in 2018, and nineteen years later in 2037 – January and March both feature two full-moon months.
In the nineteen-year lunar cycle, seven out of nineteen years harbor a blue moon, given that we define the blue moon as the second of two full moons to occur in a single calendar month. Only in years where February has no full moon at all will you have two blue moons in the same calendar year.
After August 2012, we won’t see two full moons occurring in a single calendar month again until July 2015. In the meantime, don’t forget to enjoy the first of the month’s two full moons tonight, as this lovely August full moon lights up the nighttime from dusk until dawn!
Full moon image credit: h3_six