This movie takes place during the last night of the creature's 28 day feeding spree. It's established in both the original and the sequel that every 28 years, he awakens to feed for those 28 days.

At the end of the movie, when one of the teens asks how long ago the old man supposedly killed the creature he responds "In 3 days, it'll be 28 years." Thing is, if the 28th anniversary of the "killing" was coming in 3 days, then it means the creature would have would have already been awake for 25 days!