The world change is not active every day but the chance is very high. In a Discord group we have with some friends, we share the World Board state daily after server save and I went back in time a little bit to check the records of our world:
It is now 25th January and since 26th September (both included) the event was active a total of 98 days out of the 122, which gives it an observed chance of 80.33% to appear.
This is as far as our records go and we didn't miss a single day. The sample size is not optimal but you can assume a 75-85% chance to appear, or a very nice 80% chance.
Since we have not checked the camps physically I don't know the chances of each specific camp out of the 4 possibilities.