In this episode, Kevin watches as the astronauts aboard Apollo 8 film the earth while orbiting the moon. However, the Earth is shown in full color. The Arnolds actually do not have a color TV, as revealed in Episode 9, where Wayne and Kevin attempt to persuade their father to buy them a color television. So the Earth should actually be shown in black and white.
Kevin feigns illness and stays home from school, noting that Apollo 8 enters its orbit around the moon later that night. Apollo 8 did that on Christmas Eve, 1968. Not only would Kevin have been on Christmas vacation, his house also should have been decorated for the holidays.
The Apollo 8 launch (that Kevin's class watched) was on 21 December 1968. Kevin's narrator later says "Tuesday the 8th." The next Tuesday the 8th would have been April 1969.
As Kevin tries to pluck up the courage to phone Lisa Berlini, the rest of the Arnold family are watching a television broadcast of pictures beamed from the surface of the moon. This is in color, but the Arnold family did not own a color television until the early 1970s.
The television announcers state that President Kennedy promised to send a man to the moon back in 1960; however, he wasn't inaugurated until 1961, and gave that speech on May 25, 1961.
A seventh grade student is seen carrying an S.A.T. test prep book. The S.A.T. is generally not taken until the junior or senior year in high school.