How did Rizhu come from?

Ancient arithmetic was divided into four columns: the year column, the moon column, the sun column and the time column, and then after the Universiade, when the pattern was determined, numerology deduction could be made.

The sun column refers to the day when people representing the main branches of the lunar calendar were born. Trunks and branches are recorded every 60 days. Because months are different from leap years, trunks and branches need to find a perpetual calendar.

In horology, the sun column starts clockwise from midnight to midnight, with twelve hours as a day, and each hour accounts for two hours. The dividing line between day and day is midnight, which is eleven o'clock in the evening. Before eleven o'clock is midnight the day before, and after eleven o'clock is midnight the next day. Please pay special attention to this point, and don't think that midnight is the dividing point of the day.

Ancient arithmetic was divided into four columns: the year column, the moon column, the sun column and the time column, and then after the Universiade, when the pattern was determined, numerology deduction could be made.

How to calculate the solar column is a complicated problem, because in the formulas handed down from ancient times, there are only the methods of starting from the moon in a year and starting from the morning, that is, knowing the annual column and calculating the time column, but there is no method of calculating the solar column. Because the general numerology students must master the annual column within 200 years, the solar column is easy to know, and with the formula, you can know the solar column by looking at the perpetual calendar, and you can know it by knowing the solar column.

The blind fortune tellers of past dynasties could not know the solar column by looking at the perpetual calendar, so they had a set of formulas for calculating the solar column besides memorizing a large number of calendars, but they generally swore at school that they would not tell anyone except their children and the blind.