
20. Full Moon
When the Moon can be fully seen from Earth, we have reached the Full Moon phase. Full Moon occurs when the Earth is perfectly positioned between the Moon and Sun. When this happens, the nearest side of the Moon is entirely lit by the Sun and looks like a perfect round disc.
The Full Moon phase happens about once per month. As the new Moon marks the beginning of the month in the lunar calendar, the full Moon tends to fall on the 14th or 15th day. This leads to a month in the lunar calendar being either 29 or 30 days long.