Constellations are determined by the date of the solar calendar. 1March 23, 977, the Gregorian calendar date is May 10, and the constellation of that day is Taurus.
Lunar calendar:1March 23, 977
Branch: Ding Siyi Ding Mao
Gregorian calendar:1may, 977 10 Tuesday Taurus
Source: Hua.com.