I have this app called "sun surveyor". Based on your GPS coordinates it gives you all the information. Sunset, civil twilight, nautical twilight, and astronomical twilight. It's not 100% dark until astronomical twilight ends, which (at least this time of year) isn't until 1.5 hours after sunset. But most people would call nautical twilight night, you need lights to drive and everything. 

Aluelkville on 11/7/2015
Sunset: 4:38 PM
Civil Twilight ends: 5:08 PM
Nautical Twilight ends: 5:41PM
Astronomical Twilight ends: 6:13 PM
Day Length: 10h 8m 47s

Sun Surveyor also gives you all this information for sunrise, and lots of other information like golden hour, blue hour, solar noon, and many other things.