Morning is more definitely the best time. It helps you lose weight faster to. Don't ever exercise at night, it keeps you up and sleep is really important for fat loss and toning. Early in the morning is the best time (:
It is whatever time you want to and can work out. The only benefits shown from different times are people's ability to keep the habit. I like working out in the afternoon, Night isnt a good choice you want at least a solid hour or more between working out and getting ready for bed so you sleep better. I would suggest not being one of those people in the gym at 11 pm. besides that it is up to you.