In astronomy, the New Moon is the first phase of the Moon, when it lies closest to the Sun in the sky as seen from the Earth. More precisely, it is the instant when the Moon and the Sun have the same elliptical longitude. The Moon is not normally visible at this time except when it is seen in silhouette during a solar eclipse.
The original meaning of the phrase New Moon was the first visible crescent of the Moon, immediately after conjunction with the Sun. This takes place over the western horizon in a brief period between sunset and moon-set, and therefore the precise time and even the date of the appearance of the New Moon (by this definition) will be influenced by the geographical location of the observer. The astronomical New Moon, sometimes known as the Dark Moon to avoid confusion, occurs at the moment of conjunction in elliptical longitude with the Sun, when the Moon is invisible from the Earth. This moment is unique and does not depend on location, and in certain circumstances actually coincides with a solar eclipse.
The New Moon in its original meaning of first crescent marks the beginning of the month in lunar calendars such as the Muslim calendar, and in lunisolar calendars such as the Hebrew calendar, Hindu calendars, and Buddhist calendar. But in the Chinese calendar, the beginning of the month is marked by the Dark Moon.
Although the new moon is typically depicted as a black circle, its actual phase is a very thin crescent, because the moon does not pass directly in front of the sun (except during an eclipse).
People generally wait for new moon to start new works as it is symbolic of new beginnings.