The Ban Soc Ceremony, also known as the calendar distribution ceremony, was one of the important rituals of the Nguyen Dynasty, taking place annually on the 1st day of the 12th lunar month. This ritual was initiated during the reign of Gia Long and the early years of Minh Mang, but it was not until the reign of Minh Mang that the Ban Soc Ceremony was organized on a large scale with clear regulations. Notably, in the year of Tan Suu (1841), Emperor Minh Mang decreed that the ceremony be held at Ngo Mon Gate – the symbol of power of the Hue Imperial City – instead of the court yard of Thai Hoa Palace as before, marking an important shift in the ceremonial space.
According to historical records, the annual task of compiling the calendar was assigned to the Kham Thien Giam (Imperial Observatory), the court's leading astronomical agency. Once completed, the calendars were distributed in a solemn ceremony to civil and military mandarins and the common people. The distribution of calendars not only helped the populace track agricultural seasons, but also affirmed the Emperor's care for the lives of his subjects, while demonstrating the supreme authority of the royal court in managing time and social order. Meticulous records in the Nguyen Dynasty Imperial Archives (Chau Ban), currently preserved at the National Archives Center I, show that the Ban Soc Ceremony was a key link in the royal ritual system, possessing both practical value and deep cultural-historical significance.



