Well...most authorities would tell you that the morning is the best time - and it is for
me as well...
When I first started getting into exercise, I would usually work out after work - especially since I was into Jazzercise. Most aerobic/cardio classes are traditionally scheduled in the late afternoon and/or evening hours, at least in my part of the world!
Like I said, I get up super early (usually between 3:30 and 4 a.m.) to work out, but on the other hand, hubby HATES exercising in the morning - he'd rather snooze when I'm gone and he has the whole bed to himself!

But - after work, I'm usually wiped out - but he really enjoys getting on his bike for an hour or so and riding in the hills.
What am I trying to say here?? --- Morning, afternoon, evening - whatever works for you - as long as you "just do it" is fine - at least IMHO.
Take care!