I don't own at Harborside, but instead at Westin St John, another Vistana resort with a similar set up. For the fixed weeks, if I'm not mistaken, your deeded fixed week is reserved for you at the 18 month point pending confirmation by you either by phone or online. So, if you own week 17, which would be April 24-May 1 in 2021 for a Saturday check in, the reservation would have been made October 24, 2019, at least at WSJ. Even if you confirm the reservation, though, you can float to an available week in the period you own if there is availability, starting 10 months from the check in date. So, if you're looking for week 10 instead, which would be March 6-13 in 2021 for a Saturday check in, you would have been able to float to that week, if it's available, starting May 6, 2020. You do have to float within the home week booking window of 8-10 months, which would have ended July 6, 2020 for that checkin date.
My understanding of how things worked at Harborside is that Phase I was sold as fixed week, fixed unit, and some of the Phase II weeks were also sold that way for customers willing to pay a premium over the regular price from the developer. Those weeks on the resale market are typically reflected that way by the seller. Also, certain weeks are considered "ultra premium" or "event" weeks. Those would be weeks 51, 52, and 7 if they use the same ones as WSJ. Those are typically more difficult to book than the regular Platinum Plus weeks (1-6 and 8-17) because those would have been the ones targeted for fixed week sales. At WSJ, there are generally slim pickings for floating to different weeks in the Platinum Plus season depending on the unit size you own because availability is dependent on another owner wanting a different week than they own, having been successful in getting it, and releasing their own week; or weeks that are either unsold inventory or HOA owned due to foreclosure. That would be less of a problem in a resort like Harborside Phase II where the fixed weeks sold were in the minority, though there may be other restrictions/availability windows for the ultra premium/event weeks that I don't know about for folks that paid more in that Phase. Bottom line is that if you really want week 52, you might have to buy week 52, but it will cost more; the same could hold true for week 51 and week 7, but someone else more familiar with Harborside specifically would need to verify that. You might occasionally get lucky and score a week 52, but that would likely mean being online at midnight Eastern Time when the booking window opens for you.
