Caleb's sleeping patterns

I don't know if it's been all the swimming lately, or fun in the sun, but Caleb has adopted some new sleeping patterns! Most evenings, when Mark is working, we take him dinner at work. Well, somewhere on the way to taking him food we must enter a sort of "sleep zone". Caleb will start to nod off in the car and then he's out for the entire night! Tonight we made a stop to Walmart on the way home, and Caleb slept the entire time we were there, in the shopping cart. When he was very little we used to rock him to sleep-but it had to be rather "hard-rocking". I guess when he's tired he's tired, no matter where he is!