The constellation is determined by the date of the solar calendar. 1March 29th, 997, the Gregorian calendar date is May 5th, and the constellation of that day is Taurus.
Lunar calendar:1March 29, 997.
Branch: Ding Chou, Chen Jia and Ding Wei
Gregorian calendar:1Monday, May 5, 997 Taurus
Source: Hua Wang.