Day Light Saving Time?

"Something I noticed last time I watched this movie. Why does it get so dark so early in River City? No way does the time frame work if this takes place over the last few weeks of June and the first few weeks of July. The longest days of the year. I mean it is a great movie and all and the only reason for the lighting being so dark is they were trying to get a Stage Show feel to the movie."---

I think that was the intention-to try to recreate a stage show setting.

The film is set in 1912, long before daylight savings time was adopted in the United States.

http://en.wikipedia.org/wiki/Daylight_saving_time_in_the_United_States

You're right that a few of the evening scenes would be somewhat lighter, but not by much. Besides, this is The Music Man we're talking about; don't look for anything resembling "kitchen sink reality" here.

Even without DST, sunset is at 7:55pm on July 4th.

Suspend your disbelief. It's a movie. There are other oddities such as
(A) Since the 48 star flag wasn't official until July 4th, 2012, where did they get them all (as well as the projector showing a slide of a 48-star flag). We never saw a 46-star flag.
(B) It's quite dark when Harold Hill is arrested, yet it appears to be dusk during the finale.