Ask your pediatrician if a small dose of Benadryl would help him to sleep a bit more the first morning and "reset" his clock. He may be too young at 6 months, but my pediatrician ok'd this technique at a year old. We just gave her a teaspoon (dose is based on weight, so be sure to consult pediatrician!) to induce a morning "nap". Within an hour she was back to sleep until around 9 am.