Black moon is a name recently (2016) given to various new moons or absences of them, within a year. It is not a term used in astronomy and there is no single accepted definition of it. Among the meanings ascribed to it are these: a second new moon that appears in the same month; the third new moon in an astronomical season with four new moons; the absence of a new moon in February; or the absence of a full moon in February. Definitions, frequency, dates Month with two new moons One use of the term is for the occurrence of a second new moon in a calendar month. This is analogous to the by-month definition of a blue moon as the second full moon in a month. February is too short for a second new moon to occur. This event occurs about every 29 months. The assignment of a calendar date to a new moon, and in which month a second new moon occurs, depends on the time zone. For example, the new moon of 2016-10-01T00:11 UTC occurs on 1 October for Europe, Asia and Oceania, making it the first of two new moons in October. However, for the Americas the date is still 30 September, making this the second new moon of September. Calculated in UTC, instances of a second new moon in a calendar month between 2010 and 2020 are: 2011-07-30 2014-01-30 2014-03-30 2016-10-30 2019-08-30 Season with four new moons Another use of the term is for the third new moon in a season that has four new moons. This is analogous to the Farmers' Almanac definition of a blue moon as the third full moon in a season with four full moons. A season lasts about three months and usually has three new moons. This event occurs about every 33 months. There is no dependency on time zones in this definition as the seasons are tied to the winter solstice. Instances of four new moons in a season are: 2012-05-20 2015-02-18 2017-08-21 2020-05-22 or 2020-08-19. This depends on the exact definition of the seasons: If northern summer is deemed to begin at the June solstice then the 2020-06-21 new moon occurs in northern summer. If the seasons are defined in quarter tropical years from the December solstice then the 2020-06-21 new moon occurs in northern spring. Month without full moon Another use of the term is