Elizabeth Taylor was born on 2:30 AM on 27 February 1932 according to her birth certificate.
Actress Elizabeth Taylor's birth certificate was recently released on Ancestry.com. This image comes from their Consular Reports of Births, 1910-1949, which can be searched on Ancestry.com's site.
Taylor's father, Francis Taylor, was born in Springfield, Illinois--her parents were citizens living in London at the time of her birth. He signed her birth certificate as shown in this post. Taylor's mother was Sara Warmbrodt, was born in Arkansas.