It depends if the sperm found the egg. If it didn't then she's not pregnant. If it is she's been pregnant since the time the sperm found the egg.
The first day of spring in 1996 is March 20, 1996.
The first day of spring in 1960 was March 20.
March 20 1959 was a Friday.
March 20 1967 was on a Monday.
March 20 1964 was a Friday.
March 20 2010 was a Saturday.
March 20 2009 was a Friday.
March 20, 1933 was a Monday.
March 20 1961 was a Monday.
March 20 1989 was on a Monday.
March 20, 1990 fell on a Tuesday.
March 20, 1934 fell on a Tuesday.