If you have moved to another game world, the former world disappears your character information page exactly 180 days from start to end date, not including the end date. I found a CM reply that states 6 months but it's exactly 180 days as I tested this since I have a lot of experience in world transfers. Please note, there are some websites that can still make it possible to locate a character's old former world.
In my test, I world transferred a character named New York on August 11th, 2020, and on February 7th, 2021 her former game world is not appearing on her profile anymore! I was checking back often to give you an exact answer.
Time calculation: It is 180 days from the start date to the end date, but not including the end date. Or 5 months, 27 days excluding the end date. So as you can see, it isn't exactly 6 months, but goes based on 180 days! Proof of when my character world transferred-
Source of time and date calculator (Unsupported)