I have a world that I am intending to give about an 18° axial tilt. I know generally that this will reduce seasonal variation in the length of daylight (sunrise to sunset), however, what I'm unsure of is exactly how to go about calculating it precisely at any given latitude.
The planet also has a 154 day orbit around its sun, which I don't think matters but just throwing it out there in case it does. 24 hour rotation. About the same distance to the sun, again, not sure that matters.