The problem being that the mood of the next scenes of leading to Threepio getting blasted seem to place it right after landing (no cut away, Leia doesn't change her clothes etc) but they have brighter views through the windows than darker ones.

That's why I've always thought they landed early in the morning.

But does it make any difference?

Dawn and dusk look very much alike and for all we know he city may move around the planet and get to clip the terminator several times a day.

How long is a day on Bespin anyway?

It's not Earth.