Must not get dark out there till 10:00p.m. Actually I should know since I come through there (ElPaso) a couple times a year on my way to Las Cruces and Roswell, NM. but I never paid attention. Just kidding about 10:00 but 9:00p.m. is a definate reality being so far west in the central timezone.
9:30 is normal for twilight during mid summer.