Don’t sweat it. Just be forthright with your future employer and prepare for the worst possible case. If that worst case scenario is intolerable to you then change what you can to meet your goal. Dal is hiring mil guys up to a year out so there’s precedent for delaying a start date; if you wish to change an availability date from what u represented before then just make sure it passes the reasonableness test. Btw, we here do not qualify as arbiters of ‘reasonable’ so keep your privacy and ask someone else you trust.