[Bella:] [Charlie] glanced past me into the house; his eyes were a little wild for a minute as he stared around the big, bright room. Everyone was still there… There was no evidence that the day was coming to a close. (26.47)
Charlie senses that the atmosphere in the room is supernatural, because no one in the room acknowledges that the end of the day is drawing near. So it's his human perception of time that tips him off.