At 72 degrees North, Summit is within the Arctic Circle. The sun doesn’t set for much of the summer, however since the Solstice on June 21, it’s slowly been sinking lower during the night. At the Poles the sun circles with almost no change in degree above the horizon between noon and midnight. Here we’re 18 degrees from the Pole so it follows an ellipse, sinking closer to the horizon in the night and swinging high into the sky during the day. While it still isn’t getting quite dark enough to see stars it’s definitely becoming dusky.
Today the sun rose at 3:27am and will set at 9:41pm, though it stays fairly bright throughout. Here’s a good page to check out for more information on weather and such: Summit Almanac and Weather. The nights are getting longer by 12 minutes each day!
To make your own chart by either your city or latitude and longitude check out this page.