Chinese astrology is based on a 12-year cycle. Each year of the Chinese zodiac is represented by an animal and pertains to different characteristics of the person born under the sign. The personality of the person born the animal sign is usually compared to the characteristics of the animal during the Chinese year.
The Chinese astrology is based purely on the calendrical cycle and is not based on the constellations as in the Western zodiac. The Chinese astrology however represents the five major planets as elements (metal for Venus, wood for Jupiter, water for Mercury, fire for Mars, and, earth for Saturn).
The Chinese zodiac is a 60-year cycle using the 12 original animal signs and the five elements. In addition to that, the elements may be a yin or a yang. As a rule in determining this, if the year ends with an even number it is a yang; if it ends with an even number, it is a yin.
In order to achieve good fortune in the Chinese astrology, there should be a balance of the elements and the yin and yang in a person. In order to balance this, the year, the month, and the day the person was born has to be taken into consideration. Since each element is associated with a body part, color, direction, season, and planet, these are also being considered when suggesting how to balance the yin and the yang.
Although it is popularly known that the Chinese astrology is based on the year that the person was born, the month, day and hour of birth of the person also affect his or her characteristics.