Welcome to the Q&A Forum

I looked at your campaign, and you've essentially got two options here: (1) You could add a unique element to the title tag, like the availability date. (2) You could canonicalize or de-index the variations. Keri's warning is correct about the home-page, but it looks like this is a stand-alone page and rel-canonical would be viable. That would clean up your index gradually, but it would also remove the individual availability pages from the search index (and ranking contention), so it does depend a bit on your strategy. For the site 9K pages, is quite a bit. The other thing you could do is change the system to only create links for dates with available events. I notice you have a lot of blank dates. Linking those serves no purpose, either for users or Google (and is just creating worthless pages, essentially). If you did that, a lot of these would clean up over time. You might also consider just blocking the calendar links at some point - in other words, go back 3-6 months, but then don't bother. Don't make Google crawl 5 years worth of past dates.