Nope not at all, no clock change. Admittedly, my first game I did, just to check things out faster but now I have three games on the go and haven't changed the clock at all. Besides, last time I did that in my first game, without thinking, I found all my Fish Tycoon fish had starved to death. Kind of forgot that game would be affected too. I haven't changed it since.

Besides, my other two games I've had many island events in each, and all three games were started at the same time.