It is the most important celebration in Vietnamese culture. Tet celebrates the arrival of spring and is generally celebrated on the same day as Chinese New Year, except when the one-hour time difference between Vietnam and China results in new moon occurring on different days. Many Vietnamese spend New Year’s Eve (January 31st) following rituals of cleaning the house, doing laundry, preparing special dishes to place on the ancestor altars, etc. prior to midnight. On the first day of the new year, they follow customs such as visiting homes, ancestor worship, wishing New Year's greetings, giving lucky money in red envelopes to children and elders, and opening a shop. Celebrations start the day before and continue for three days.