Full moon is called a blue moon. The term "blue moon" used in this sense may date to as early as the 16th century, but it became well known in the United States due to the "Farmers' Almanac" (published since 1818). According to the "Farmers' Almanac", a "blue moon" is the third full moon in any period between either solstice and equinox, or between equinox and solstice, (calculated using the mean tropical year), which contains four full moons. These seasons are equal in length, unlike the astronomical ones, which vary in length depending on the Earth's speed in its elliptical orbit round
Splitting of the moon describes an actual event at the time of the Prophet, but it clearly refers to the end of the world. Some Muslim scholars argue that an astronomical event must have happened at that time, which made it appear as if the moon had been split in two, because the phenomenon was seen at least in India as well. One such possible lunar event could be a large asteroid hitting the moon, and the plume and debris from the strike blocking enough lunar view to make it appear as if the Moon had split in two. A second possibility could be