A.M.
It sounds like he is overtired when he gets home. He may need two naps and longer naps. Where does he nap at the sitters? Is it quiet? He could also go to bed earlier. Also maybe he is finding his sitters environment stressful in some way.
Also, he may be saying that he wants more time with you when you all get home. I would skip preparing dinner and just play with him. I take my main meal in the middle of the day and then just grab a snack when I get home. This means that I can hang out full time with my little 20 month old when I get home until she goes to sleep. At that age, they are pretty much a full time job :)
I definitely wouldn't do time outs. First, they are not advised for children younger than 3 and second, he sounds stressed and the last thing you should do with a stressed little one is abandon them with a harsh discipline technique that was originally devised as a way to train pidgeons.