Constellations are determined by the date of the solar calendar. 1990 The Gregorian calendar date on the 16th day of the first lunar month is February 1 1, and the constellation of that day is Aquarius.
Lunar calendar: the 16th day of the first month of the Year of the Horse.
Main branch: Gengwu Wuyin Ding Wei.
Gregorian calendar: 1990 February 1 1 Sunday Aquarius
Source: Hua.com.