The Last of the Time Police: The Time Authority Book One

Some careless littering by a pair of time travelers sets off a Chronological Anomaly that may lead to the destruction of modern history. Our Time Line’s only hope: those same bungling Time Police, who are sent back to clean up their mess before the world as we know it ceases to exist. To succeed, Stan and Jack need the assistance of Benjamin Franklin in order to find a displaced Leonardo DaVinci.