In astronomy, the term black moon is neither well-known nor frequently used. The Black Moon --- Changeable by date and time; A Black Moon occurs when there are two dark cycles of the moon in any given calendar month. It is believed that the second dark moon is a time of great power within the spiritual world and any magick worked during this time is especially powerful. It has also occasionally been applied to at least four different situations:

In myth and folklore the full moon of each month is given a name. In many cases the waxing moon and waning moon are also given names. There are many variations, but the following list gives the most widely known names:

The third full moon in a season with four full moons is called a blue moon, as described in the Maine Farmers' Almanac. Until recently it was commonly misunderstood that the second full moon in a month was the blue moon. However, it was recently discovered by Sky & Telescope magazine and reported on NPR that the interpretation of a blue moon as the second full moon of the month was erroneously reported in a 1946 issue of Sky & Telescope and then perpetuated by other media.^{[citation needed]}