In the Christmas episode in season 2, Kevin and Wayne try to convince Jack to buy a color television for Christmas. In an episode in season one (Angel #1.4), Kevin is seen watching a color TV in his living room.
In episode 41, Kevin comes home from school to watch the liftoff of Apollo 13. Apollo 13 lifted off on Saturday, April 11, 1970.
Throughout the series, whenever characters are seen riding in vehicles, there are often instances of late-eighties to early-nineties vehicles appearing in the distant background.