140 days is the cutoff for TDY. Lets say you hit the 120 day mark (20 days left) but you still have 4 weeks of school. They will recompute and say "he has another 48 days left, which is less than 140, so he can continue to get per diem. That's how guys can go longer than 140 days and still receive per diem. If they were to recompute at the 20 day mark, and there's like 4 weeks left, they would say "he has 168 days left, so now this is a PDS" and per diem goes away. I had found this in the JFTR so later on I'll try to find it again and post the chapter number. But now that I think about it, with 140 days being the cutoff, and my orders being written to reflect 139 days for API (which technically is only 42 days), it seems like they did it so that I could draw per diem if I have to. Wow, {sniff} the Navy loves me!