There was a multiplayer RTS called arkaron or something that featured time travelling. The gameplay was built around building up your forces to fight at a particular point in time. As you built up you sent units back in time to battle opposing forces in waves with a limited amount of energy. The game ran on a constantly ticking timeline that implemented changes in the timeline (spawned units) at the end of each timeline section. The original idea was to be more expansive with the implementation but it had to be cut down.