time of evening
When do you think it ends? I don't think they ever really specify, but I always feel like it's around midnight, which explains why there are so few people on the streets, and really the only thing that comes close to justifying why Laurie was turned away from the house when she was screaming for help, especially if it was a more innocent time.
But in the sequel, I believe they mention it's something only like 9, probably to explain why there are more scenes early on featuring other people in other areas of town.