Believe it or not, we actually operate on a 25-hour cycle. This means that when we are trying to get our babies (4-plus months) on a good sleep schedule, we will run into the occasional bump in the road. The best thing to do is keep your baby as well rested as possible, pay attention to his temperament and be flexible with his naps and bedtime.
If he usually has his first nap at 9 a.m. there may be a morning every couple of weeks when he will be tired before then (we’re assuming that everything else has remained the same). When this happens, don’t be too concerned about keeping him up until exactly 9 a.m. No need to be too rigid when we’re only talking about a few minutes!