The constellation is determined by the date of the solar calendar. The date of Gregorian calendar September 8 1986 is 10, 1 1. The constellation of that day is Libra.
Lunar calendar:1September 8th, 986
Branch: Bing Yin Wuzi of the Reform Movement of 1898.
Gregorian calendar:1986101October1Saturday Libra.
Source: Hua.com.