Cahill's 2012 managerial merry-go-round began at Bolton with boss Owen Coyle before then Blues boss Andre Villas-Boas signed him for £7m in January.
Roberto Di Matteo then replaced AVB when he was sacked in February but the Italian didn't last much longer.
He was controversially sacked and Rafa Benitez hired as his successor last week.
As for England, 26-year-old Cahill began 2012 trying to impress Fabio Capello but will end it aiming to stay in Roy Hodgson's thoughts.
Cahill told the Daily Star: "Yeah, it has been a crazy year for both club and country. The changes of managers is what it is.
"There is an element of obviously getting involved with one manager and then, like you say, you are on trial again and everyone's got a different opinion.
"Every manager has got a different opinion and I just have to keep working as hard as I can and hope you can impress people enough to be given a chance.
"It is never going to be a situation where you go through your career under one or two managers.
"So you have to adapt and learn from each one and try to improve your game."