For me it's been evening since always. The reason is simply that I don't get up too early. If I do sometimes, I don't feel like putting my body to work. In the evenings my body itself becomes more active to go for a workout, I mean I don't feel reluctant in the evening. I think this may be one case with so many people. 

IamSINGLE

HealthAndFitness

When is the best time to exercise to get the most from your workout?

I found a couple of research articles (didn't keep the references, though) about that topic, but centered about clinical patients (can't remember what they had, exactly).  They concluded that patients showed significant but moderate more benefits when exercising latter in the day compared to the morning.   I remember I thought "of course they do because the evening is the hardest moment to exercise!".  (Well, at least for me it is. :-)