Something I've always found interesting about Young Frankenstein is the way it transitions from the present day to the thirties or earlier.
The lecture room scene clearly takes place in the present day, looking at the costumes, decor, and the number of women med. students.
Freddy then boards a steam train to journey to Transylvania. The Transylvanian costumes and the one car we see suggest an even earlier time.
Young Frankenstein's black and white photography actually makes this less jarring than it might have been