You are allow one transfer (either in or out) per UY per membership ID. It's not by calendar year, and not by 365 days. You can make 2 separate transfers (in or out) for 2021 UY and 2022 UY at the same time... A trade of points for the same UY won't work, since you can transfer out and in on same UY.
You can only transfer out the current UY points you are in, and the next UY. Likewise, the person receiving the transfer can only receive points in the current UY they are in or the next UY, so it doesn't always line up.
For example, you have Feb. UY, so you are in 2021 UY, and other person has Dec. UY, so in 2020 UY currently, since Dec. 2021 isn't here yet.
So, you can transfer out your 2021 UY points or 2022 UY points, but other person can only receive points in 2020 UY and 2021 UY.
In this case, only 2021 UY can move to other person.
Likewise, if you looking to receive points, other person can only transfer out 2020 and 2021 UY points, and you already past 2020 UY, so can't receive 2020 UY points from other person, you can only get 2021 UY points. To get 2022 UY points, the other person UY for 2021 must start already. For this reason, it's hard to swap/trade points.
Hope that makes sense.
Great3