This I know for sure...

Everything I've read recommends not exercising late in the day because it can make it difficult for you to fall asleep. I've been using a rowing machine for 30 minutes every day around 5:00pm. I've had no problem falling asleep. In fact, I usually feel more tired after I exercise than before. It seems like I yawn a lot after I exercise too. Maybe I'm just different  than the average person.