Hopefully this game is fun!
The Idea is: If you could change or witness one moment in time what would it be...it could be that you are doing this for yourself, family, a loved one, a friend, the world, etc.
In both situations (change or witness) you have to travel in time (either backwards or forwards), in the case of change you also have to say how you would change or prevent that moment from happening. In the case of witness, you are just an observer and your presents will not impact the future.
I would travel back to the Dakota Apartment in New York City on December 8, 1980 and inform the doorman to alert the NYPD that the man standing across the street was carrying a gun and intends to kill John Lennon on his return. Mark David Chapman would be arrested for carrying a concealed weapon...
I would travel back to see what woodstock was all about. Gotta be honest it looked like a nightmare.