What's the best time to work out during the day?

Morning. Research indicates that morning exercise has the most benefit on weight loss. However, don't let a conflict stop you from exercising. Any exercise is better than none!
Just Do It. This has been something studied for a number of years. My conclusion. The best time for you. Personally I like to wake up and I find mid morning or mid day the best. As long as you get your activity in daily that is the important thing.