This thirty days has confused many a Bible scholar throughout the years, but I dare say that I have never heard nor read anyone's explanation, that is backed up by scripture, which explains this beyond an educated guess. If the thirty days extends beyond the Tribulation, which I doubt, then it is not a part of it. I tend to think that it is part of the Tribulation, and that in a serious study one might conclude that the 1290 spoken of by Daniel ends at the 2520th day and begins thirty days before the middle of the Tribulation.
Either way, the Tribulation is 2520 days by way of the type of the Jewish Wedding tradition. Since we're the Bride of Christ I think that would make much more sense. Should Pastor Riley's rapture day come and go, then perhaps he might consider removing that thirty days from his calculation, which would place the rapture around November 6-7 according to his calculations.
I'll be happy if it turns out to be anywhere near these dates
.... which I personally tend to think are in the general timeframe.