Although this film is set in the year 1972, the partygoers at Ed and Kate's party are dancing to the Sherbert song "Howzat", which was not released until 1976.
Although the film is set in the 1970s, the "Clipsal" type electric light switch seen on the bathroom wall in close up in one scene dates from the 1990s.
One of his whiskey bottles has a barcode. Barcodes in this form were not adopted until 1973 and were not used on products until 1974. The scene is set in 1972.