when you have finished your prereqs study for the DAT. Depends on your study habits. I would recommend studying about average 1-2 hrs a day for a month or two to get your feet wet, then study hardcore 5-7 hours a day for 1-2 months. I personally don't think its that good of an idea to plan to study for 5 months straight 10 hrs a day. I ythink that's a bit unrealistic. I prefer more realistic goals, they are more easy to attain.
I would study lightly for April and May then hardcore for June and then take it early July. Then you can finish your application and repeat the exam early October if needed.