The tooltip appearing after hovering over an event on the timeline shows a date one year earlier than the right-hand side slider and the event edit interface
Not really sure how as everything was working correctly when I created the timeline (already in the new format), but now something is broken
Is this event in an era? Is this era offsetted ?
Yes, in an era. Era has offset "restart dates at 0"
I think you have answered your own question there :) 0 is a -1 offset from the normal 1