I would assume it is your commission date not contracted date. If you look at it, when you retire none of your ROTC years count towards your retirement, thus your contracted date would not be the one that I would assume they will use.
If you are a senior than you would be under the old system because it is not your report date for ADAF, but the moment you take the oath.
ROTC grads will have 2 different pay dates versus SA grads. Your longevity pay date is your commission date. Your rank pay will be the avg between commission and report.
~ IE DS commissioned May. Reported 9/30. His longevity pay date is May. His DOR is July because they took the 4 months wait time and split in half, which is July. Fencers DS commissioned in May, his DOR is the date of commissioning because they are ADAF immediately.
Bullet retired 21 1/2 yrs after commissioning. However, he did not report for 10 months or just over 20 yrs ADAF. His retirement pay is not based on his contracted date from ROTC, nor is it his report date for ADAF or his DOR. It is commission date. Had it been report he would have only received 50%, not the 52.5% of his base. (2.5% per year after 20)
~ It is just a funky little loophole for ROTC grads. Even though you may be on casual status for months and not report ADAF, Big Blue still sees it as you being ADAF the minute you raise your hand.