The Vietnamese follow two calendars: Gregorian and Lunar Calendars. While Gregorian Calendar is for official work, the Lunar Calendar is mostly for traditions, spiritual life and events, and for agricultural work.
Do Temple Festival is held every year on the 15th of the third lunar month to commemorate the coronation of King Ly Thai To (Ly Cong Uan), considered one of the most visionary leaders throughout the history of Vietnam.