Please add an ability to customize when it's the evening/day/bedtime for each user. If you can already do this, please tell me.
I would also love to see this - I live and work in a time zone 8 hours ahead of the time I set my computer at. Need to keep the computer on Eastern or it screws up my calendar, so I'd love to tell f.lux that sunset is actually around "11AM"
For the time being, I recommend changing your Location in f.lux to a place where the sunset has occurred already.