The dark moon is the time when the moon is so close to the sun in the sky that it cannot be seen even near sunset or sunrise. Depending on how close the moon passes to the line between earth and sun, this may be anywhere from 1.5 to 3.5 days long. The middle of this period is the astronomical new moon; the term is used to distinguish it from the crescent new moon, which was the original meaning of the term "new moon" and is the next phase after dark moon.
