Season End on Later Servers

So, my friends have been playing a while and the season is about to end. I intended to join them, but their server was full, so I joined another.

Then I noticed their server ends in a few days, but mine is only on week two. What happens with the season end for servers that didn't start at the same time?

Am I not going to be able to transfer this character to their new world? Do I have to start over?