The game was played with a whole bunch of cards with historical events on them. Each event had two versions, one on each side of the card, and you could travel through time turning cards over to representing altering the past, in order to achieve some goal given to you at the beginning. Certain events contradicted each other, however, and when they both existed this created a paradox. If enough paradoxes occurred the timeline would explode and everyone lost.
Can anyone identify this game for me?