Rizhu, in eight words, actually represents the day when a person was born, with branches of the lunar calendar.
The daily records of the trunk and branches are circulated every 60 days. Due to the different months and leap years, it is necessary to find a perpetual calendar for the trunks and branches every day. The sun column, in the words of life science, starts from midnight to midnight clockwise, with twelve hours as a day, and each hour takes up two hours.
The dividing line between day and day is midnight, that is, eleven o'clock at night. Before eleven o'clock is the last day of Shihai, and after eleven o'clock is the next day.
Please pay special attention to this point, and don't think that midnight is the dividing point of the day. Sun column is one of the four columns, which is a way of calculation chosen by ancient numerologists.