There is no straight answer. There are gaps between BMT and CCSC, between each of the schools in the Pipeline and sometimes phases in STTS. Failures, set backs, injuries, even natural disasters could all happen. Then there is availability of slots for a JTAC Qualification Course and then the individual's ability to progress through training at his unit and the availability of that training at his unit.
Bottom line; at least 6 months after getting to your first Duty Station upon completion of the Pipeline. Probably closer to a year after you get there.