The lunar cycle of phases is about 29.5 days. As the moon rotates and revolves around the earth, and the earth rotates and revolves around the sun, the shadows cast by the shifting positions of the moon and earth cause the moon to wane, wax, and "disappear". This is known as the lunar cycle.
What's a lunar cycle ? -- If you use a star in the sky as a marker, the moon passes it every 27.32 days. -- If you go by the phases of the moon, the time between two occurrences of the same exact phase is 29.53 days.
Lunar eclipses can only happen at the FULL moon phase. And whether you see it or not, there's a new moon every 29 days, and a full moon 14.5 days later. That's been happening for the last few billion years.
Well, there are approximately 29.5 days in a lunar phase period, from new moon to new moon. So I would assume that there would be 29.5 days between each particular phase as well. But I am not 100% sure about that.
The Waning Phase in the lunar cycle occurs as the moon shrinks from the Full Moon to the New (Dark) Moon. Note: You can tell when you are in the Waning Phase when the Left Side of the Moon is illuminated. Conversely, if the Right Side is illuminated, the Moon is Waxing.