The method of calculating the start of major luck is divided into yang years and yin years. Yang years are Jia, Bing, Wu, Geng, and Ren. Yin years are Yi, Ding, Ji, Xin, and Gui. For a male born in a yang year or a female born in a yin year, the calculation should be done in the forward direction. For a male born in a yin year or a female born in a yang year, the calculation should be done in the reverse direction. The specific method of arranging the major luck is based on the stem and branch of the birth month, and it can be arranged in either the forward or reverse direction. First, calculate the age at which the major luck starts. For a male born in a yang year or a female born in a yin year, count the days from the day of birth to the next solar term, without considering the intermediate terms, and then divide the number of days by 3. The quotient is the age at which the major luck starts. If there is a remainder, the remainder should be converted using the following rules: 3 days equal 1 year, 1 day equals 4 months, 1 hour equals 10 days, and 1 hour equals 5 days. For a male born in a yin year or a female born in a yang year, count backward from the day of birth to the previous solar term and calculate the number of days. Then divide by 3, and the quotient and remainder together give the age at which the major luck starts. It is important to note that there are 24 solar terms in the lunar year, with one solar term and one solar node per month. The twelve solar terms are as follows: January starts with Start of Spring, February with Awakening of Insects, March with Clear and Bright, April with Grain Full, May with Grain in Ear, June with Slight Heat, July with Limit of Heat, August with White Dew, September with Cold Dew, October with Start of Winter, November with Great Snow, and December with Minor Cold. The other twelve are the solar nodes: January with Rain Water, February with Spring Equinox, March with Grain Rain, April with Grain Full, May with Summer Solstice, June with Great Heat, July with Limit of Heat, August with Autumn Equinox, September with Frost's Descent, October with Minor Snow, November with Winter Solstice, and December with Great Cold. These are known as the nodes. Each month has one solar term and one node, making a total of 24 solar terms in a year. When calculating the Eight Characters, the solar terms should be used for calculation, not the nodes. The principle of determining the start of major luck is to count the number of days from the day of birth to the next solar term. Then divide this number by 3 to get the age at which the major luck begins. This is the method of calculating the start of major luck. For example, if a person was born on the 20th of the second month of the year Ren Wu at the hour of You (3-5 PM), this is the Qing Ming (Clear and Bright) solar term. On the 20th of the third month at noon, it is the Start of Summer (Lixia). The person was born between these two solar terms. Counting forward, it is the Start of Summer, while counting backward, it is the Qing Ming. Since this man was born in a yang year, he should go to the next solar term. From the 8th of the third month, count the number of days to the 22nd of the third month when the Start of Summer occurs. This is a total of 14 days. Divide 14 by 3 to get 4 with a remainder of 2 days. Two days equal 8 months. Therefore, the person's major luck starts at 4 years and 8 months old, meaning that the start of his major luck should be calculated from 4 years and 8 months of age.

In addition to calculating the age at which the major luck starts, it is also necessary to determine the stems and branches of the major luck. The stems and branches of the major luck are determined based on the stems and branches of the birth month (the month pillar). If the age at which the major luck starts is calculated in the forward direction, the next month's stem and branch should be used as the starting point and continued in the forward direction. For example, if the birth month is Jia Chen, the subsequent stems and branches would be Yi Si, Bing Wu, Ding Wei, Wu Shen, Ji You, and so on. Below is an example to illustrate this.
Step 1: First, arrange the four pillars (Four Pillars of Destiny) based on the birth time. For example:
Example of major luck calculation 1: A man born on the 8th of the third month at noon in 1942 (lunar calendar)
Nian (Year): Ren
Yue (Month): Jia
Ri (Day): Yi
Si (Hour): Ren
Nian (Year): Wu
Yue (Month): Chen
Ri (Day): Si
Si (Hour): Wu
Step 2: Calculate the age at which the major luck starts. According to the principle that a male born in a yang year should proceed in the forward direction, count the number of days from the day of birth to the next solar term, then divide by 3. The result is the age at which the major luck starts. In this case, from the 8th of the third month at the hour of Wei to the 22nd of the third month at the hour of Wu, the date of Start of Summer is on the 22nd of the third month at the hour of Wu, which is a total of 14 days. Dividing 14 by 3 gives 4 with a remainder of 2 days. One day equals 4 months, so the remaining 2 days equal 8 months. This results in 4 years and 8 months, meaning the person starts major luck at 5 years old according to the rule of rounding up.
Step 3: Arrange the person's life path. Based on the principle that a male born in a yang year proceeds in the forward direction, the major luck starts from the next stem and branch after the birth month. The birth month is Jia Chen, so the next stem and branch is Yi Si. Starting at the age of 5, the major luck is "Yi Si", followed by "Bing Wu", "Ding Wei", "Wu Shen", "Ji You", and so on. Each major luck lasts for ten years, so the ages would be as follows:
5 years old, 15 years old, 25 years old, 35 years old, 45 years old, 55 years old, 65 years old, 75 years old
Yi, Bing, Ding, Wu, Ji, Geng, Xin, Ren
Si, Wu, Wei, Shen, You, Xu, Hai, Zi
After arranging the major luck, use the stem of the day pillar as the standard. Write down the six relatives of the stems and branches of the four pillars, where a yin stem meets a yang stem or a yang stem meets a yin stem is considered "zheng" (positive), while a yin stem meets a yin stem or a yang stem meets a yang stem is considered "pian" (negative). Then, based on the combination of the four pillars, analyze the good or bad fortune of each major luck by examining its stems and branches.
Example of major luck calculation 2: A man born on the first day of the ninth month at the hour of Zi in 1952 (lunar calendar). First, list the eight characters:
Nian (Year): Ren
Yue (Month): Geng
Ri (Day): Wu
Si (Hour): Ren
Nian (Year): Chen
Yue (Month): Xu
Ri (Day): Xu
Si (Hour): Zi
A male born in a yang year proceeds in the forward direction. In 1952, the solar term of Start of Winter occurred on the 20th of the ninth month at the hour of Xu. From the first day of the ninth month at the hour of Zi, count forward to the 20th of the ninth month at the hour of Zi, which is 19 days. Dividing 19 by 3 gives 6 with a remainder of 1. One day equals 4 months, so the remainder of 1 day equals 4 months. Thus, the person starts major luck at 6 years and 4 months. Additionally, from the hour of Zi to the hour of Xu, there are 10 hours. One hour equals 10 days, so 10 hours equal 100 days. This is approximately 3 months and 10 days. Adding this to the age of 6 years, we have 6 years plus 9 months (from the birth month) plus 4 months (from the 1 day) = 6 years + 13 months = 7 years and 1 month. However, since the exact time of the solar term is the 20th of the ninth month at the hour of Xu, the actual start of major luck is on the 11th of the fourth month of 1959. The arrangement of major luck for this person is as follows:
7 years old, 17 years old, 27 years old, 37 years old, 47 years old, 57 years old, 67 years old
Xin, Ren, Gui, Jia, Yi, Bing, Ding
Hai, Zi, Chou, Yin, Mao, Chen, Si

Each major luck governs the fortune or misfortune of ten years. Within those ten years, there are ten different stems and branches, and these ten stems and branches may have various relationships such as mutual generation, mutual assistance, or mutual suppression. These ten stems and branches may also influence the stems and branches of the four pillars. Therefore, merely calculating the major luck is not enough; it must be combined with the current year (流年). "Current year" is also called "the year of the heavenly ruler." It refers to the year of the person's birth, regardless of whether it is a yin or yang year, or whether it is a male or female. For example, if a person was born in the year of Jia Zi, then Jia Zi is the first year of the current year, Yi Chou is the second year, Bing Yin is the third year, and so on until the end of life. There are two main purposes of calculating the current year: first, to determine the events of each year from birth to death; second, to answer the question of whether a particular year is auspicious or inauspicious. For example, if someone asks about the fortune in the 45th year, the current year's stem and branch can be calculated from the birth year, and then analyzed in combination with the eight characters and the major luck to determine the fortune and misfortune of that year.