Assume that your average adult works 9-5, and your average school child is in school 8-3. Broad strokes, these are the two groups to focus on. I know most adults commute earlier than 9, and most students are up earlier than 8, but it's safe to say that most Americans are up-and-at-'em from 8-5.
On the shortest day of the year in Boston, sunrise is at 7:10am and sunset is at 4:14PM. Including civil twilight ("it's still kind of daytime") extends it to 6:38am to 4:46PM.
Even on the shortest day of the year, if you wake up even before 7 you're waking up in daylight. But, sunset is super early. Every working adult is commuting home in actual nighttime.
Shift that forward 1 hour, and it gets light at 7:30AM and gets dark at 5:45PM. While slightly darker for students in the morning, it's immensely better for working adults, who at least get some daylight in the evenings, and not actual nighttime before 5PM.