This was supposed to be during the first season of "The French Chef", in 1962. In their New York hotel room, there's a touch-tone telephone beside the bed. Touch-tone telephones were first introduced in November of 1963.
When Paul asks for an extra blanket, Avis gets a green plush fleece blanket (with a stitched edge on top) out of the closet. Synthetic fleece didn't appear until 1981. Back then, it would have been a heavy woven cotton or wool blanket edged with a wide satin ribbon on the top end.
In an establishing shot of Manhattan, the Frank Gehry tower at 8 Spruce Street is seen on the left of the screen. That building was constructed in 2010, about 50 years after the events of this episode were to take place.