Constellations are determined by the date of the solar calendar. The solar calendar date of February 1975 is March 25th, and the constellation of that day is Aries.
Lunar calendar: February 13, 75.
Main Branch: Gengwu, Yi Mao Bazaar.
Gregorian calendar: Tuesday, March 25th, 1975 Aries.
Source: Hua.com.