Heavenly Stems and Earthly Branches
Heavenly stems and earthly branches are collectively known as Stem-Branch or Gan-Zhi. The 10 heavenly stems are Jia, Yi, Bing, Ding, Wu, Ji, Geng, Xin, Ren and Gui. The 12 earthly branches are Zi, Chou, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu and Hai. Each heavenly stem is paired with an earthly branch to form the Gan-Zhi sexagenary cycle that starts with Jia-Zi (Table 2).
Table 2 The Gan-Zhi sexagenary cycle.
1
|
2
|
3
|
4
|
5
|
6
|
7
|
8
|
9
|
10
|
11
|
12
|
Jia-Zi
|
Yi-Chou
|
Bing-Yin
|
Ding-Mao
|
Wu-Chen
|
Ji-Si
|
Geng-Wu
|
Xin-Wei
|
Ren-Shen
|
Gui-You
|
Jia-Xu
|
Yi-hai
|
13
|
14
|
15
|
16
|
17
|
18
|
19
|
20
|
21
|
22
|
23
|
24
|
Bing-Zi
|
Ding-Chou
|
Wu-Yin
|
Ji-Mao
|
Geng-Chen
|
Xin-Si
|
Ren-Wu
|
Gui-Wei
|
Jia-Shen
|
Yi-You
|
Bing-Xu
|
Ding-Hai
|
25
|
26
|
27
|
28
|
29
|
30
|
31
|
32
|
33
|
34
|
35
|
36
|
Wu-Zi
|
Ji-Chou
|
Geng-Yin
|
Xin-Mao
|
Ren-Chen
|
Gui-Si
|
Jia-Wu
|
Yi-Wei
|
Bing-Shen
|
Ding-You
|
Wu-Xu
|
Ji-Hai
|
37
|
38
|
39
|
40
|
41
|
42
|
43
|
44
|
45
|
46
|
47
|
48
|
Geng-Zi
|
Xin-Chou
|
Ren-Yin
|
Gui-Mao
|
Jia-Chen
|
Yi-Si
|
Bing-Wu
|
Ding-Wei
|
Wu-Shen
|
Ji-You
|
Geng-Xu
|
Xin-Hai
|
49
|
50
|
51
|
52
|
53
|
54
|
55
|
56
|
57
|
58
|
59
|
60
|
Ren-Zi
|
Gui-Chou
|
Jia-Yin
|
Yi-Mao
|
Bing-Chen
|
Ding-Si
|
Wu-Wu
|
Ji-Wei
|
Geng-Shen
|
Xin-You
|
Ren-Xu
|
Gui-Hai
|
The use of Gan-Zhi to record the years, months, days and hours all started in different periods in history. The Gan-Zhi years and days have been used for two to three thousand years. In ancient time, the months and the hours (the hours are called shichen) were named after the earthly branches only (Figure 1 and Table 3). Through the years, people started to make stems of the months after the stem of the year (Table 4), and stems of the hours after the stem of the day (Table 5). The Gan-Zhi's of year, month, day and hour together form the Eight Characters.
Table 3 The relationship between the 12 shichen and the present time system.
12 shichen
|
The present time system
|
Zi hour
|
23 hour to 01 hour
|
Chou hour
|
01 hour to 03 hour
|
Yin hour
|
03 hour to 05 hour
|
Mao hour
|
05 hour to 07 hour
|
Chen hour
|
07 hour to 09 hour
|
Si hour
|
09 hour to 11 hour
|
Wu hour
|
11 hour to 13 hour
|
Wei hour
|
13 hour to 15 hour
|
Shen hour
|
15 hour to 17 hour
|
You hour
|
17 hour to 19 hour
|
Xu hour
|
19 hour to 21 hour
|
Hai hour
|
21 hour to 23 hour
|
Table 4 The relationship between the stem of the year and the stem of the month.
The stem
of the year
|
The stem of the month
|
Yin
1st
month
|
Mao
2nd
month
|
Chen
3rd
month
|
Si
4th
month
|
Wu
5th
month
|
Wei
6th
month
|
Shen
7th
month
|
You
8th
month
|
Xu
9th
month
|
Hai
10th
month
|
Zi
11th
month
|
Chou
12th
month
|
Jia or Ji
|
Bing
|
Ding
|
Wu
|
Ji
|
Geng
|
Xin
|
Ren
|
Gui
|
Jia
|
Yi
|
Bing
|
Ding
|
Yi or Geng
|
Wu
|
Ji
|
Geng
|
Xin
|
Ren
|
Gui
|
Jia
|
Yi
|
Bing
|
Ding
|
Wu
|
Ji
|
Bing or Xin
|
Geng
|
Xin
|
Ren
|
Gui
|
Jia
|
Yi
|
Bing
|
Ding
|
Wu
|
Ji
|
Geng
|
Xin
|
Ding or Ren
|
Ren
|
Gui
|
Jia
|
Yi
|
Bing
|
Ding
|
Wu
|
Ji
|
Geng
|
Xin
|
Ren
|
Gui
|
Wu or Gui
|
Jia
|
Yi
|
Bing
|
Ding
|
Wu
|
Ji
|
Geng
|
Xin
|
Ren
|
Gui
|
Jia
|
Yi
|
Table 5 The relationship between the stem of the day and the stem of the hour.
The stem
of the day |
The stem of the hour
|
Zi
hour |
Chou hour
|
Yin hour
|
Mao hour
|
Chen hour
|
Si
hour |
Wu hour |
Wei hour |
Shen hour |
You hour |
Xu hour |
Hai hour |
Jia or Ji |
Jia
|
Yi
|
Bing
|
Ding
|
Wu
|
Ji |
Geng |
Xin |
Ren |
Gui |
Jia |
Yi |
Yi or Geng |
Bing
|
Ding
|
Wu
|
Ji
|
Geng
|
Xin |
Ren |
Gui |
Jia |
Yi |
Bing |
Ding |
Bing or Xin |
Wu
|
Ji
|
Geng
|
Xin
|
Ren |
Gui |
Jia |
Yi |
Bing |
Ding |
Wu |
Ji |
Ding or Ren |
Geng
|
Xin
|
Ren
|
Gui
|
Jia |
Yi |
Bing |
Ding |
Wu |
Ji |
Geng |
Xin |
Wu or Gui |
Ren
|
Gui
|
Jia
|
Yi
|
Bing |
Ding |
Wu |
Ji |
Geng |
Xin |
Ren |
Gui |