Why is the auspicious day of the ecliptic classified as fierce?

Although a certain day is an auspicious day, there are good days and bad days at a certain time of this day. It doesn't mean that the ecliptic day means a good day. Similarly, the day of the underworld does not mean that it is a bad day. It also has a good time period. Choosing a date means' taking things as the key link and taking God as the purpose', that is, choosing an auspicious day and auspicious party according to what you want to do.