Dont know if this helps but here
Moon phases represent the names given to points in its orbit around Earth. Each phase lasts for only an instant as the moon constantly moves. To the naked eye, the full moon lasts about three days, but in reality, it is a full moon for just an instant before it begins to wane. The moon takes just under one month -- an average of 29 1/2 days -- to complete its phases.
TL;DR (Too Long; Didn't Read)
As the moon passes gradually and continually through its monthly cycle, each phase lasts only an instant. The Full Moon, for example, is simply a point halfway between waxing gibbous and waning gibbous.
Phases of the Moon
The moon has eight phases: new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter and waning crescent. But it is not as simple as dividing 29 1/2 by eight to find out how long each phase lasts. The fraction by which the moon is illuminated steadily increases or decreases at all times.
Primary and Intermediate Phases
The primary phases of the Moon cycle are the new moon, the first quarter, the full moon and the last quarter. The dates and times of these phrases -- which you can calculate or find on calendars -- change from month to month according to the positions of the Sun and the Moon. Astronomers refer to the crescent and gibbous phases as intermediate phases.
