This section describes how years are counted in Chinese calendar.
In Chinese calendar, a year is defined as a tropical year or solar year, which is the time for the Sun to return
to the same position along the ecliptic circle as viewed from the Earth. This is the same definition as the Western calendar.
But in Chinese calendar, years are counted with a combination of two numbering systems:
When counting years, elements from both Heavenly Stems and Earthly Branches are used continuously in cycles.
The first year is 甲子 (jiazi), the second is 乙丑 (yichou), and so on.
At year eleven, the first element 甲 (jia) of Heavenly Stems will be used again.
So the eleventh year is 甲戌 (jiaxu).
Of course, the thirteenth year is 丙子 (bingzi), because the first element of
Earthly Branches is used after the last element.
Since the numbers 10 (Heavenly Stems) and 12 (Earthly Branches) have a common factor of 2, only 1/2 of the 120 possible
stem-branch combinations actually occur. The resulting 60-year (or sexagesimal) cycle takes the name jiazi (甲子)
after the first year in the cycle, being the Heavenly Stem of "jia" and Earthly Branch of "zi".
The starting point (epoch) for the Chinese calendar is 2697 BCE. So year 2007 in Western calendar is the year 4704
in Chinese calendar.
Here is a map to help you convert years between the Chinese calendar and the Western calendar:
