Read the following passage and answer the questions:

Tet holiday is celebrated on the first day of the Lunar New Year in Viet Nam. Some weeks before the New Year, the Vietnamese clean their houses and paint the walls. New clothes are bought for the occasion. One or two days before the festival, people make Banh chung , which is the traditional cake, and kinds of jam. On the New Year's Eve, the whole family gets together for the reunion dinner. On New Year morning, all the members of the family pay their respects to the elders by beautiful words. In return, they receive lucky money wrapped in red tiny envelopes. Then people go to visit the neighbors, friends and relatives.

When is Tet holiday celebrated in Viet Nam?

........................................................................................................