mistake in the opening credits
When they show all the stuff in Dr. Loomis's home office, it shows Laurie's yearbook photo, and says Class of '78. This can't be correct. Canonically, the original took place Halloween of '78, meaning she would've been class of '79.
My guess is this was done intentionally because too many people would be thrown off by the 19-year difference when it was the 20th anniversary. Sad they think so little of our intelligence. But they're probably right.