Terrible costume design.
The costume design is all over the period map - from 1932 to 1942 to, well, 1976!
Really, it's only been on for an hour and I've seen women wearing those white satin dresses that were all the rage in the early thirties, the costumes from "Casablanca" (1942), and things that a gal could have worn to work in 1976, when the film was made.
Since I assume this movie was made to appeal to the sort of person who liked old movies, I can't believe how careless they were on that front.
“Seventy-seven courses and a regicide, never a wedding like it!