The New Moon on the first day of the New Year-- the full moon 15 days later The Chinese calendar is based on a combination of lunar and solar movements. The lunar cycle（月运周期）is about 29.5 days. In order to catch up with the solar calendar the Chinese insert an extra month once every few years (seven years out of a 19-yearcycle). This is the same as adding an extra day on leap year （闰年）. This is why, according to the solar calendar, the Chinese New Year falls on a different date each year. New Year's Eve and New Year's Day are celebrated as a family affair, a time of reunion and thanksgiving. The celebration was traditionally highlighted with a religious ceremony given in honor of Heaven and Earth（万物）， the gods of the household and the family ancestors. The sacrifice to the ancestors, the most vital of all the rituals（仪式）， united the living members with those who had passed away. Departed relatives are remembered with great respect because they were responsible for laying the foundations for the fortune and glory of the family. The presence of the ancestors is acknowledged on New Year's Eve with a dinner arranged for them at the family banquet table. The spirits of the ancestors, together with the living, celebrate the onset of the New Year as one great community. The communal feast called surrounding the stove or weilu. It symbolizes family unity and honors the past and present generations.