I don't think it matters too much whether it's sunrise or sunset either, but your physics on gas giants are completely wrong.

Bespin if far from mostly oxygen. It has a habitable zone 30 miles deep, according to official information. And anyway, gas giants just don't work that way. They are far too dense when you go deeper into them, the gases become thicker until they become liquid. Some gas giants will have a solid core. And light would NOT go through even if it were all oxygen. The duration of sunsets and sunrises has nothing to do with the composition of the planet (in the way you suggest), and everything to do with its rotation. The only reason both might be longer is if the planet rotates on its axis more slowly than Earth does. And while you might assume that would be the case, as gas giants are so much bigger than human-habitable planets like Earth, that's not true either. Quite the opposite in fact. Jupiter has the shortest "day" of all eight planets, at about 9.9 hours, and Saturn's is second shortest, followed by Neptune and Uranus. So, days on Bespin are actually likely to be shorther than a standard (Earth) day.