There's a reason the Four Pillars of Destiny in Japanese Astrology is so accurate: It's incredibly specific and complex! But it's not so hard to learn if you understand the elements involved and how they work together.
Each of the Four Pillars has a "Kan-Shi" (10 Heavenly Stem signs and 12 Animals known as Earthly Branches), 12 Fortunes, and Decade luck, which are all calculated together to determine your personality traits and fate.
What is Kan-Shi?
The term "Kan-Shi" describes two cycles. The first, "Jikkan," is your Heavenly Stem sign, which is one of 10 combinations of either Yin or Yang and one of the five elements Wood, Fire, Earth, Metal and Water.
The second cycle is "Junishi," which describes the 12 Animals (Earthly Branches) that are also calculated into your sign.
Jikkan is the fundamental theory of Yin-Yang, which is the principle that all things in this world can be differentiated into two sides: Yin and Yang. For example, the Sun represents Yang, the Moon represents Yin. An odd number represents Yang, an even number represents Yin. The front surface of something two-sided represents Yang, the back side represents Yin.
When you combine the idea of two Yin-Yang sides with the five elements, you get a total number of 10 signs -- also known as the 10 Heavenly Stems. For example, Wood and Yang represents Kinoe; Wood and Yin represents Kinoto; Fire and Yang represents Hinoe; Fire and Yin represents Hinoto.
From there, the 10 signs can be assigned with elements of the birth year, month, day and time, too. The cycle of the signs begins with Wood and Yang = Kinoe and ends with Water and Yin = Mizunoto, before coming back and starting from Kinoe again.
To illustrate, the year 2012 was represented by Water and Yang (Mizunoe); and the year 2013 is Water and Yin (Mizunoto). In 2014 it will cycle to Wood and Yang (Kinoe), and by 2022 it will be the year of Mizunoe once again. And this same cycle is attributed not just to the year, but also to the day, month and time. Which means you could have a Mizunoto year with a Kinoe month and a Hinoe day … and each combination adds up to a unique interpretation.
Junishi is the second cycle of Kan-Shi, which describes the 12 animal signs that belong to each year, day month and time. These are the same animal signs we are familiar with from Chinese Astrology: Rat, Ox, Tiger, Hare, Dragon, Serpent, Horse, Sheep, Monkey, Cock, Dog and Boar.
The 12 Fortunes represent the energy flow through the stages of human life from infancy to old age, and their unique qualities are calculated together with the Jikkan and Junishi to complete your character profile.
Putting It All Together
In a Four Pillars of Destiny chart, each of the Four Pillars is represented by two characters because every moment in time (year, month, day, hour) is defined by two elements.
The first character shown is the Heavenly Stem, the second is the Earthly Branch. Remember, there are one of each for each of the Four Pillars!
The 10 Heavenly Stem signs and the 12 Earthly Branches can be calculated into a combination of 60 patterns.