Narrator: I realized then, that there were special things a man says to a woman.
(Kevin dials a phone number)
(He slams down the phone)
Narrator: I also realized I had no idea what those things were.
Kevin: Dad, I'm calling about returning a tie.
Narrator: As he looked at me, I knew we both sensed the cycle of family history poignantly repeating itself.
Jack: Since when do you wear ties?
Kevin fakes being sick with the flu and stays home from school before finally getting the nerve to call Lisa Berlini, the same night that Apollo 8 entered its orbit around the moon. Apollo 8 did that on Christmas Eve, 1968. School would have been out and there should have been Christmas decorations all over the place, not to mention some kind of holiday celebration at the Arnold home. Not to mention we find out in later episodes that the Arnold's have an annual Christmas party.
Kevin mentions that "Tuesday the 8th" was the day he bumped into Lisa Berlini in the hallway. In 1968, "Tuesday the 8th" was in October, and if the show did actually take place in December of that year, then Dec. 8, 1968 would have fallen on a Sunday. This is also 2 weeks before the Apollo 8 mission.