I forgot to add a bit of mindless trivia: we see Marty's watch at some point (I think he's babbling on about when the vest goes 'boom'). It shows the episode takes place on Tuesday the 8th.

Due to the air date of February 24, 1971; that leaves 1970 or very early 1971 for possibilities. In 1970, Tuesday the 8th happened in September and December. In 1971, it doesn't happen until June! It gives us an idea/ballpark when the episode was filmed and it certainly wasn't done in a single day.

Happy 50th!