Black moon years. When February is without full moon, then the preceding January or December and the following March or April have two full moons. As with the case of two new moons in a month, whether a black moon by this definition occurs depends on the time zone. Calculated in UTC, instances of a month without full moon between 1990 and 2040 are: Another use of the term is for the absence of the new moon in a calendar month. This can occur only in February; it happens about every 19 years. When February is without new moon, then the preceding
Orbit of the Moon associated with the lunar orbit. The sidereal month is the time it takes to make one complete orbit around Earth with respect to the fixed stars. It is about 27.32 days. The synodic month is the time it takes the Moon to reach the same visual phase. This varies notably throughout the year, but averages around 29.53 days. The synodic period is longer than the sidereal period because the Earth–Moon system moves in its orbit around the Sun during each sidereal month, hence a longer period is required to achieve a similar alignment of Earth, the Sun, and the Moon.