My last two batches were carbed @ 40 degrees and 14 PSI, and both had good carbonation in 5-7 days. No rocking or shaking, just set it and forget it. My PSI was slightly higher than yours, but I don't imagine 1 PSI would make much difference. My LHBS told me to expect ~10 days at this pressure/temp, but I've not had to wait that long so far for good beer.
As for calculating the estimated time, I have no clue. I've never been more scientific than just sampling every few days.