Diana hands Ivan her invitation to the reception while the two are on the train. He reads it, holding the rectangular card horizontally (landscape mode). But in close-up the card is printed and held vertically (portrait mode).
The date on the invitation for Ivan's reception states Monday, July 6th, 1916. July 6th that year was on a Thursday.
The story takes place in 1916, but all the women are coiffed and gowned in the style of 1931.