Herong's Notes on Astrology and Horoscope - Version 2.11, by Dr. Herong Yang
Chinese Horoscope and Eight Words
This section describes how to calculate the Eight Words based on a person's birth date and time.
In Chinese horoscope, a person's destiny is calculated based on the person's Eight Words (八字 bazi). Which represent the person's birth date and time.
Here is how to calculate a person's Eight Words:
1. A person's birth date and time is divided into Four Pillars (四柱 shizhu): Year (年 nian), Month (月 yue), Day (日 ri), Hour (时 shi).
2. Earch pillar is represented with two words: one word from Heavenly Stems, and one word from Earthly Branches. This gives Eight Words (八字 bazi).
3. The Year Pillar is easy to calculate. It is the same as the Chinese calendar year stem-branch name. For example, year 2007 will be 丁亥, dinghai. But there is one important difference between the horoscope system and the calendar system. In the horoscope system, new year starts on the first solar term date, 立春 Lichun, which is around February 4, not the Chinese new year date.
4. The Month Pillar is based on Solar Terms, not Lunar Months. So the first horoscope month is between the first solar term and the third solar term. The stem-branch name of each month is calculated through the following table:
Year 甲* 乙* 丙* 丁* 戊* 己* 庚* 辛* 壬* 癸* 正月 丙寅 戊寅 庚寅 壬寅 甲寅 丙寅 戊寅 庚寅 壬寅 甲寅 二月 丁卯 己卯 辛卯 癸卯 乙卯 丁卯 己卯 辛卯 癸卯 乙卯 三月 戊辰 庚辰 壬辰 甲辰 丙辰 戊辰 庚辰 壬辰 甲辰 丙辰 四月 己巳 辛巳 癸巳 乙巳 丁巳 己巳 辛巳 癸巳 乙巳 丁巳 五月 庚午 壬午 甲午 丙午 戊午 庚午 壬午 甲午 丙午 戊午 六月 辛未 癸未 乙未 丁未 己未 辛未 癸未 乙未 丁未 己未 七月 壬申 甲申 丙申 戊申 庚申 壬申 甲申 丙申 戊申 庚申 八月 癸酉 乙酉 丁酉 己酉 辛酉 癸酉 乙酉 丁酉 己酉 辛酉 九月 甲戌 丙戌 戊戌 庚戌 壬戌 甲戌 丙戌 戊戌 庚戌 壬戌 十月 乙亥 丁亥 己亥 辛亥 癸亥 乙亥 丁亥 己亥 辛亥 癸亥 冬月 丙子 戊子 庚子 壬子 甲子 丙子 戊子 庚子 壬子 甲子 腊月 丁丑 己丑 辛丑 癸丑 乙丑 丁丑 己丑 辛丑 癸丑 乙丑
For example, the Month Pillar of the first horoscope month in 2007 is 壬寅, renyin.
5. The Day Pillar has no way to calculate. It is based on a continuous count system since 722 BCE. To get the stem-branch name of a Day Pillar, you need to look at a Chinese horoscope calendar. Or you can count the days yourself from a known date. For example, given the Day Pillar of February 4, 2007 as 己巳, then the next day will be 庚午.
You also need to remember that a new day starts at 23:00 in Chinese calendar. So if you were born at 23:30, your Chinese birth day should be the next day.
6. The Hour Pillar can be calculated using the following table:
Day 甲* 乙* 丙* 丁* 戊* 己* 庚* 辛* 壬* 癸* 23-01:00 甲子 丙子 戊子 庚子 壬子 甲子 丙子 戊子 庚子 壬子 01-03:00 乙丑 丁丑 己丑 辛丑 癸丑 乙丑 丁丑 己丑 辛丑 癸丑 03-05:00 丙寅 戊寅 庚寅 壬寅 甲寅 丙寅 戊寅 庚寅 壬寅 甲寅 05-07:00 丁卯 己卯 辛卯 癸卯 乙卯 丁卯 己卯 辛卯 癸卯 乙卯 07-09:00 戊辰 庚辰 壬辰 甲辰 丙辰 戊辰 庚辰 壬辰 甲辰 丙辰 09-11:00 己巳 辛巳 癸巳 乙巳 丁巳 己巳 辛巳 癸巳 乙巳 丁巳 11-13:00 庚午 壬午 甲午 丙午 戊午 庚午 壬午 甲午 丙午 戊午 13-15:00 辛未 癸未 乙未 丁未 己未 辛未 癸未 乙未 丁未 己未 15-17:00 壬申 甲申 丙申 戊申 庚申 壬申 甲申 丙申 戊申 庚申 17-19:00 癸酉 乙酉 丁酉 己酉 辛酉 癸酉 乙酉 丁酉 己酉 辛酉 19-21:00 甲戌 丙戌 戊戌 庚戌 壬戌 甲戌 丙戌 戊戌 庚戌 壬戌 21-23:00 乙亥 丁亥 己亥 辛亥 癸亥 乙亥 丁亥 己亥 辛亥 癸亥
Adding all Four Pillars together, you will get the Eight Words. For example, if a person was born at noon time on February 4, 2007, his or her Eight Words will be 丁亥壬寅己巳庚午.
If you don't want to do the calculation yourself, you can try to get a Chinese horoscope software to help you. Here is a picture of horoscope Eight Words displayed on a calendar day produced by a software:
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