Manual Sunset/Sunrise Time Settings
First let me say that f.lux is 75% of why I jailbreak. Using f.lux on all of my displays has changed my quality of life/work tremendously.
The iOS app behaves unpredictably for me. My location is above the arctic circle (66degN) and f.lux does accurately find, but it doesnt always transition from day/night correctly. Sometimes it will transition quickly back and forth, taking 5ish seconds each way. This behavior was more pronounced a couple of weeks ago, closer to summer solstice, leading me to believe that maybe f.lux doesnt know what to do when the sun doesnt set.
If the iOS app had a daylight schedule plot, like the windows application, with a manually settable location, it would really help diagnose and resolve the issue.
Thanks for your note - that's a tough area to be on a solar schedule -as we move the other versions to a circadian schedule that will help you a lot I think.