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. 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 and are: . 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:  . Another use of the term is 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.