Vietnam's New Year is celebrated according to the Lunar calendar. It is especially known as Tet Nguyen Dan, which begins when date changes from Tet. It lasts from January twenty-first to February nineteenth. The exact year to year. Vietnamese people usually make preparations for the holiday several weeks beforehand. They tidy their houses, cook special food, clean and make offerings on the family altars. On the New Year's Eve, people sit up to midnight to see the New Year in, then they put on new clothes and give one another the greetings of the season. Tet lasts ten days. The first three days are the most important. Vietnamese people believe that how people act during those days will influence the whole year. As a result, they make every effort to avoid arguments and smile as much as possible.