All the caresheets I've come across suggest that breeding usually occurs in winter during the early months of the year. However I've often seen people advertising snakes that were born very late in the year. I just picked up a female myself that was born at the end of October 05. Doesn't that suggest that breeding occured during the summer?
Also, since annual rhythms in most species are dictated by changes in temperature or the length of the day, how do snakes kept in basements or other enclosed rooms with no environmental cues for the season outside "know" when it's winter? Given the artificial environment, if you manipulated the lighting schdedule and temperatures and then introduced a male why would it matter whether it was January or July?