They form patterns that do not change, night after night and year after year.
Shepherds and farmers, in prehistoric days, studied these patterns because they served as a calendar.
The moon went through its phases twelve times [per year] while the sun traveled through the constellations once.
In other words, there are twelve months to the year and the sun spent one month in each of twelve constellations.
It was calibrated to track the waxing and waning phases of the moon, used as a method for counting years, months, days and hours in the Chinese imperial court and civil calendar, and utilized to forecast one’s future and determine one’s character.