When did you get paid after being frocked?

I was frocked for E-4 from the September cycle, and I know I don't get paid for E-4 until after 6 months. My question is when does that 6 months start? Did it start when people were taking exams in September? When the results were released in November? Or did it start when I was frocked? I'm asking because I get BAH once my LES says I'm being paid as an E-4.