Zodiac sign of April 20th 1985?

That is a Taurus.

however each year is different and the day the sun enters Taurus can vary by 1 or 2 consult an ephemeris for the time change It is a table of astronomical readings showing planetary positions A trained astrologer can observe the way a person acts or read physical features to decide what sign you are especially at the changeover or cusp And there is no blending of signs at the cusp-your either one or the other