Lunar New Year Festival (Lunar New Year Festival, Tết cả, Tết ta, Tết âm lịch in Vietnamese) is the first festival to open a lunar new year. The festival lasts from the 23rd day of the twelfth lunar month of the previous year to the 7th of the first lunar month in the New Year. The festival is characterized with many solemn rituals and ceremonies at the royal court and among the common people. During this time, all activities are temporarily stopped for the sake of ancestral worship, relaxation, family reunions and visits, and good-luck wishes and congratulations.
During the Lunar New Year Festival, a number of ceremonies are held in order to show off the royal court’s solemnity and authority. Under the Lê Dynasty, before the festival, there were such rituals as the calendar issuing ceremony (lễ ban lịch), the procession of the earthen spring buffalo and the Herder-god (lễ tiến xuân ngưu), the ceremony of cleaning and storing royal seals (lễ tảo loát ấn phù), the ritual of raising the New Year pole (lễ thướng tiêu). Other ceremonies which took place during and after the festival include: the ritual held at the New Year’s Eve (lễ trừ tịch), the worship ritual on the 1st morning of the New Year (lễ Chính đán), the ancestral worshipping ceremony during three main the Lunar New Year festival day, the Heaven-worshipping ceremony (lễ tế giao), the ceremony of lowering the New Year pole (lễ khai hạ), the royal seal-opening ritual (lễ khai ấn), the ceremony held at the royal ancestral temple to ask for blessings at the beginning of the year (lễ Bảo thần) and the ceremony to wish the King longevity (lễ Khánh thọ).
Under the feudal dynasties, a king considered himself the Son of Heaven, the link between the heaven and the common people, and he was responsible for making the calendar so that the folk could know the time and solar terms for farrming, ceremonies and life. Under the Lý Dynasty the Chính Dương Pavilion was established for temporal and calendrical calculation. The Trần Dynastry established a specialized agency (Thái sử cục). Astronomer Đặng Lộ created the Hiệp Kỷ Calendar to replace the old one. Under the Lê Dynasty, the court used the Khâm Thụ Calendar and established the Imperial Observatory (Tư Thiên giám). The ceremonies of offering the calendar to the King and presenting the calendar to courtiers were organized. The Nguyễn Dynasty removed the imperial capital to Phú Xuân, used the Hiệp Kỷ Calendar, established the Royal Observatory (Khâm Thiên giám) and organized the calendar-giving ceremony (lễ ban sóc).
Administered by the Ministry of Rites, Tư Thiên giám (Imperial Observatory) was the central agency in charge of weather forecast, selecting good dates, fengshui, and most importantly, calendrical calculation. Tư Thiên giám consisted of nine pepople, including a Director (Thiên lệnh giám), a Deputy (Phó giám), an Assistant Director (Giám thừa), an assistant astronomer (Thần lang), and five astronomers (Ngũ quan chính). From the second lunar month, Tư Thiên Giám observed and calculated the time when the Sun and the Moon rose and set; divided time by date and hour; and compiled the calendar for the New Year. The calendraical calculation required seriousness and accuracy.