What is the period time twilight took place?

I think it was March - April in the movie, as Bella said: 'It's March. The middle of semester.', when she first arrived to Forks High School. And when Mike asked her to the prom, he told her it was a month away, and the movie ended with the prom. Though when Edward was in Bella's room, he said that he has went there for the last couple of months, so the timeline is a bit confusing.