Hyatt told me GOH applied to stays with a 12/31/24 check out date should have the elite night credited in 2024 (even if it takes until Jan for it to post). If I end up applying it for a res with a 12/31 checkout day, I'll be able to confirm or deny this

I applied it for a friend with a checkout of 12/29, so unfortunately, I won't be able to know for sure if a 12/31 check out would credit to 2024 or 2025. But, as I mentioned above, the Hyatt rep I spoke with seemed pretty confident that it would be 2024. But who knows...