Time Enough

A trio of time travelers from the 29th century were sent back to 2005, 2017 and 2029 respectively to investigate a small town in California. A small town with an unusually large amount of traces of closed timelike curves created between 2000 and '30 by an unidentified time traveler. But, their whole mission went amiss as soon as they arrived and are now stuck, 800 years in their past.