Other mistake: When Ben smashes the face of the ghoul trying to walk through the kitchen door, he comes back in and locks the door. But, when he drags the body of the ghoul he killed in the house out that same door and lighting it on fire, he runs back in, slams a small table against it but never re locks it. So until he boards it up, that door is left unlocked. That little table wouldn't stop anyone. (00:18:45 - 00:20:00)
Other mistake: Ben drags the body of the ghoul he killed in the house out the kitchen door. As he drags it out you can see he leaves it on the porch and lights it on fire, which would certainly set the wooden porch on fire and probably the rest of the house. But, once the flames are huge, you will see that the body has moved down onto the grass. But Ben never pushes it down off the porch. (00:19:45)
Other mistake: After the truck blows up, when Ben picks up the torch and starts to fight back to return to the house, several parked vehicles can be seen behind the ghouls. (01:12:40)
Other mistake: In the 30th Anniversary version with new footage it is revealed that the first zombie we see (the one that kills Johnny) died in the electric chair. If that's the case, he should be bald with a large burn on his scalp, but he has a full head of hair.
Other mistake: A few minutes after Tom and Judy have been killed in the truck and their bodies burned by the fire, the zombies begin to eat some of the body parts. One of the zombies can be seen with a human hand that appears to be neatly severed and unaffected by the fire, surely the hand would have been so badly burned by the fire beyond all recognition.
Other mistake: When the cemetery ghoul loses his grip on Barbra's rolling vehicle a parked car can be seen in the rear passenger window that wasn't there before. Ten seconds later a van or truck can be seen from Barbra's driver side window.
Answer: No. Each is a progression of several weeks or years.
Captain Defenestrator