Why is the constellation updated?

It depends on the season and the revolution and rotation of the earth, so it will be a little different. If calculated according to the lunar calendar, then the date of the constellation is also different.

The interval between constellations is unknown to most people. According to the fixed date, especially the intersection time, there is no other way to check the constellation. The easiest way is to use the lunar calendar and take the 24 solar terms as the fixed point.

Constellations originated from western astrology, so we can't use the solar calendar to calculate the lunar calendar. If calculated according to the lunar calendar, the date of the constellation will be different every year.