Blanche's marriage to Laurence and her tryst with Philip all occur in May 1853. A sheriff's notice states that the trial concluded in July 1860, but it had to still be 1853 because Blanche's pregnancy was not yet obvious.
The published date of Philip's execution is said to be a Tuesday when it was actually a Monday (or a Saturday, if the stated year was corrected).
The story is set from January 1853 to August 1860, yet Lavinia is the same age throughout the film.