You know how I
hate to contradict people... but actually, I think morning
is the best time to exercise, and early evening. Basically, when your metabolism is slow you need to give it a kick start. For the same reason you should always have breakfast!
As for what exercise to do, well just put on some Jimmy Smith and strutt your stuff. Just don't let the neighbours see.
Good luck. And remember "You're not fat, you're cuddly".