The Chinese Calendar is a solilunar calendar. It integrates as well the revolution of the Earth around the Sun as the movement of the Moon around the Earth.
A month begins at the day of the new moon (invisible Moon) and ends at the day before the next new moon. The full moon is either on 15 or 16 of the month.
A Chinese year can have 12 or 13 lunar months, that correspond to the nomber of new moons between two successive winter solstices. The year is appelé leap year if there are 13 months in the year.