Easiest way for me to remember it all is to first think of the UY the trip will happen. A December 2023 trip takes place in your August 2023 UY.
All trips can be booked with banked points from the UY prior to the trip, points from the UY of the trip, and borrow, up to 50% of points from the UY after the trip to complete the reservation.
Points need to be in that status when you go to book.
So, that trip can use your banked Aug 2022 points, 2023 points, and any borrowed 2024 points, up to the 50% you might need. When you go to make the reservation, it would give you the option to bank right then. But, I do it ahead of time because I never want to take too long when making an 11 month booking, especially if it is during a very busy time...and December is definitely one of those times!