The Sino-Vietnamese calendar is divided in cycles of 60 years which combine celestial “trunks” (can) and earthly “branches” (chi).
The position of 12 animals of Zodiac in Vietnam Calendar.
The 10 can are, in order, giap, at, binh, dinh, mau, ky, canh, tan, nham, and quy. The 12 chi, each connected with an animal of the zodiac, are ty (rat), suu (buffalo), dan (tiger), mao (cat), thin (dragon), ty (snake), ngo (horse), mui (goat), than (monkey), dau (rooster), tuat (dog), and hoi (pig). The first year of each 60-year cycle is named Giap Ty, combining the first can with the first chi; the following year is called At Suu, and so on.
The 3rd year of the Hong Bang reign (2877 BCE) is considered the Giap Ty year of the first cycle of Vietnamese history. Historical events are dated according to the year’s title and the reigning name of the king: for instance, the Binh Than year of the Thinh Duc reign, or 1656 AD under King Le Thanh Tong. As months are also counted in this fashion, the combination of can and chi often serves to designate a date of birth. Months are also counted in this way, beginning with the 11th lunar month of the previous year (Ty), the 12th (Suu), and so on.
For instance, the first month of the At Dau year (2005) is called the Giap Dan month. The same formula is also used to denote days and hours; see fortune-telling, horoscopes. Common saying: Chagn biet At, Giap gi (to know neither At nor Giap): to understand nothing at all.
