Constellations are determined by the date of the solar calendar. The Gregorian calendar date of April 1990 in the lunar calendar is May 1 1, and the constellation of that day is Taurus.
Lunar calendar: April 90 17.
Main branch: Geng Wuxin Fourth Soldiers.
Gregorian calendar: 1990 May 1 1 Friday Taurus
Source: Hua.com.