I remember reading a history book about the Battle of Midway (No, I don't remember the name any more.) that mentioned that the IJN ran on Tokyo Time no matter where they were. As the fleet included transports carrying soldiers to invade Midway after "dealing" with the USN, the soldiers, mostly poorly educated peasants, were left wondering why the sun was rising at 3 AM. Now, imagine what it would be like for children who never bothered to go to school if we try year-round DST again. That's not an argument against the idea, just an observation about one of the side effects of doing so.