Some food for thought for any of you who might fall under this.This change to the US code for FY 2009.
For 3 years prior to seeing the light and going to Navy AOCS, I was in both the Army Reserve and Army ROTC under their Simultaneous Membership Program. There was a law/regulation that stated that any time spent in an officer producing program while concurrently serving in another capacity could NOT be counted toward pay longevity or retirement. What this meant for me was that when I commissioned, I commissioned as a O-1 over 0 years instead of an O1 over 3 years. It also meant I lost about 16 months active duty credit toward retirement from my Army Reserve boot camp, AIT, summer training (I usually did 8 weeks vice 2), etc.
The around 1996-97 they changed the law. The time now counted. The new law did not say anything about it being retroactive or non-retroactive. Of course PSD said non-retroactive. I appealed to DFAS and about 2 months latter got one HUGE retro-pay check. They went back to day 1 of my time in the Navy and recomputed my pay. (I actually got pretty lucky as I was TAD to EUCOM at the time it showed up and I was in Bosnia which was a tax-free area. Timing is everything.) Plus when I retired a year latter, I had the 16 months of active duty back and added to my Navy time.
Follow this carefully and look to see what it says about being retroactive. It could be big dollars for you.