Harry catches the Hogwarts Express at 11 am at King’s Cross Station, where he is helped by Molly Weasley and encounters several members of the Weasley family. He and his fellow students then travel until evening to Hogwarts. Harry properly meets Ron Weasley and they share a compartment; he and Ron immediately become friends. He also meets Hermione Granger and Draco Malfoy, but they don’t hit it off.
A trip by rail from London to the Highlands of Scotland can take 8-11 hours, depending on the route. The Hogwarts Express leaves at 11 am and doesn't arrive until after dark, which would be at least 8:45 pm, since sunset on that day was 8:16.