It seems that setting the world date changes the timeline date abbreviation but only from a point onward. It's not the before 0 or after 0.
There are 3 abbreviations in this order: A.I., A.P. and P.P.
The current era is in the P.P. calendar, but when I set the world date to year 137 P.P. It changes the abbreviation for the A.P. era but not the A.I. era
Setting the Abbreviation in "after year 0" on the world, changes abbreviations even in years before year 0.
Timeline and World Date
Hi! The problem is that you appear to have duplicate eras with the same name and duration but different content. Here is what I want you to do. Switch your timeline to list mode. The go through it and find the duplicate era. Consolidate all the data in one era and delete the other one. That should fix all your problems. I already tried it with one of your duplicates because that era had no content. I may have change the color in The Pax era by mistake. Sorry. Let me know if this solves your issue