It's hard to say exactly what will happen, and a lot depends upon what was happenening in each game when the clock adjustments were made.
The only way to know the effect on the Island Events is to have saved the log file that contains the last event for each game. There is a way, by examining the log file, to determine when the next one should happen, but only if you save it right after an event occurs. The log file is erased and recreated each time you launch the game.
I wouldn't abandon them, though, until you determine how badly affected they are.
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Barbara
Unicorn
Last Day of Work