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
The Druid Order the Autumn Equinox, one at the Spring Equinox, and one at Summer Solstice. Sometimes the location or time varies due to current circumstance. The first public ceremony of the year, the Autumn Equinox, takes place on Primrose Hill in London. The second ceremony of the year, the Winter Solstice, passes without a public ceremony. The third ceremony of the year, the Spring Equinox, is held at Tower Hill in London. The fourth and final public ceremony of the year is the Summer solstice. This event is marked by three ceremonies at Stonehenge in Wiltshire: a simple ceremony at midnight for