for the absence of the full moon from a calendar month. This can occur only in February; it happens about every 19 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: February 1999 February 2018 February 2037 Month without new moon 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 January or December and the following March or April have two new 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 new moon between 1990 and 2040 are: February 1995 February 2014 February 2033 Paganism In some aspects of paganism, particularly amongst Wiccans, the black moon is considered to be a special time when any rituals, spells, or other workings are considered to be more powerful and effective. Others believe rituals or workings should not be conducted at these times. Criticism of terminology The term black moon is not formally established in astronomy and is used at best in the popularization of astronomy. There is no single definition of the term black moon. The new moon itself cannot be observed. The lack of a new or full moon in February can only be assigned to the month, not to any particular date; as such, this is also not observable. The event of a black moon is an artefact of how the Gregorian calendar or the seasons map onto lunations. There is no physical or geometric difference between a black moon and other instances of a new moon. See also References Wiccan terminology Astrology New moon