Full moon (this usage has been noted as "erroneous" by "Sky & Telescope" in 1999). According to either definition, "blue moons" occur with the average frequency of intercalary months, seven times in 19 years, the "Farmers' Almanac" system of "full moon names" effectively defining a lunisolar calendar. Full moon The full moon is the lunar phase when the Moon appears fully illuminated from Earth's perspective. This occurs when Earth is located between the Sun and the Moon (more exactly, when the ecliptic longitudes of the Sun and Moon differ by 180°). This means that the lunar hemisphere facing Earth – the near
Full moon were less likely. All this is relevant to canine rather than human behavior. Historically, month names are names of moons (lunations, not necessarily full moons) in lunisolar calendars. Since the introduction of the solar Julian calendar in the Roman Empire, and later the Gregorian calendar worldwide, people no longer perceive month names as "moon" names. The traditional Old English month names were equated with the names of the Julian calendar from an early time (soon after Christianization, according to the testimony of Bede ca. AD 700). Some full moons have developed new names in modern times, e.g., the blue moon,