Originally Posted by
Matt4200
Meaning checking in 12/18-12/28, checking out 12/28, and checking in 12/28-1/2 is the exact same as 12/18-1/2/21.
Yes you're right. However... it wouldn't be the first time where the first of two separate, yet consecutive, reservations posts to your account before your final check out date.
Which means that:
a) the basic nights might indeed credit to 2020
b) unless Hyatt IT automatically reverses those nights and adds them to 2021 after final check out, you then need to convince a customer service agent that nights stayed in 2020 should actually apply to 2021. There might be a fair amount of HUACA required.