The dates given in the movie are inconsistent. The telethon takes place Veterans Day weekend, November, 1957. It is stated that telethon finished on noon that Sunday, which, according to the calendar, would be November 10th. However the date on the room service bill signed the previous afternoon for Maureen is also dated November 10th. And when the duo are asked to open the New Jersey night club on November 15th, they respond they can't because that is the next day after the telethon ... and that date is inconsistent with both the calendar and the room service bill.
When Lanny and Karen are having dinner and they leave the restaurant Karen has hoop earrings in (both ears) but when she goes back and Lanny kisses her she has no earring in her left ear, though the one in her right ear is still visible and she had them both on throughout the rest of the scene.
Karen wears a ring on her right hand throughout the movie except when she leaves the hotel after spending the night with Lanny. When she addresses the concierge the ring is on her left hand.
As Lanny signs the bill in the hotel room when Maureen brings him his food, there is a ZIP code visible in the hotel's address. This part of the film is set in 1957, but ZIP codes were not used by the US postal service until 1963.
The telethon takes place in 1957. The boys sing the song "Together (Wherever We Go)" from Gypsy. But Gypsy didn't open on Broadway until 1959. And the songs weren't public knowledge until then.
When Maureen is in the bathtub talking to her girlfriend on the telephone, modern-day blow-molded plastic shampoo bottles can be seen on the ledge of the tub behind her.
(at around 39 mins) Lanny says that Sichuan food comes from Northern China. Sichuan Province is actually in Western China.