Is there a constellation between the two constellations?

Yes, the boundary of each constellation is not fixed, but it will not change in more than a day or two, which is determined by the motion law of stars. For example, Aquarius, suppose this year from 1. 2 1 to 2. 19, maybe next year 1. 2 1 to 2. 20, so the constellation depends not only on the year and month, but also on the year.