Looking back at my invoices, I can see that I usually work more hours those two months than any other months of the year.
I also get depressed from lack of sunlight in the dark Scandinavian autumn days.
On the other hand a total of one (and that was some trivial layout) bug was reported on the code I coded and shipped in that period this year.
Maybe the bugs are only found later?
That also suggests that the bugs found in October and November was introduced by the interns during the summer vacation?