The constellation is determined by the date of the solar calendar. 1990 The Gregorian calendar date of the sixth day of the eighth lunar month is September 24th, and the constellation of that day is Libra.
Lunar calendar: the sixth day of August, 90.
Branch: Geng Wuyiyou Ren Chen
Gregorian calendar:1Monday, September 24th, 990 Libra.
Source: Hua.com.