Well, techncically SA doesn't have a set date, yet, as the mentioned part is not yet published. However, Autumn seems optimal, because if it was Winter, we'd have to deal with snow till now unaccounted for and if it was Summer or Spring, it would be too early for people to say it's almost 15 years since thedude's conquest, except perhaps August.
If we were to keep the dates for both stories and say SA is on October and TDD on August, that would put a 2-3 months difference between them or a 1 year + 2-3 months difference, depending on what year's August we're talking about. One might seem too short for you, the other seems rather long to me, but manageable. If we don't wish to change the dates, I leave it upon thee to take your pick.