My response? Whatever time of day you will be CONSISTENT with.
There have been numerous studies testing the effect of exercise at various times of day. VO2max, training and tapering, energy intake, sleeping patterns; you name it, it has been tested. The conclusion has been:
"Exercise is equally effective, regardless of time of day."
Don't like the mornings? Exercise in the afternoons. Have to pick up your kids after work in the evening? Wake up an hour early and go for a run. It's all based on what works best for YOU.
*NOTE: Studies have shown that maximal exercise later in the day can have an effect on sleeping patterns. If you have trouble falling asleep at night, exercising in the late afternoon/evening might not be a good idea.