A few minutes into the show, Father is telling about his and Mother's wedding in the kitchen. Betty remarks that it sounded devoid of romance, to which Father replies, "It was not devoid of romance! It was Spring! Flowers were in bloom, birds were singing!" But at the beginning of the show, Betty finds their anniversary marked on the calendar on September 20th....which is Fall.
Margaret claims that, because she and Jim had a modest wedding, she never got to wear her grandmother's wedding dress, yet, in the episode 'The Old Days', she shows the dress to Kathy and tells her that she did indeed wear the dress at her wedding.