Question: when do yennefer and geralt meet?
Answer: Sometime 13 years before the Slaughter of Cintra: Geralt and Yennefer meet and battle a djinn (episode 5) -- which we know happens after the banquet because Jaskier helpfully recalls Geralt invoking the Law of Surprise. Geralt and Yennefer's paths cross again to confront a golden dragon sometime after that (episode 6).