From the ancient humanoids of four billion B.C. to the Kelvan Invasion of the 123rd century, all time stands open for you. All Our Yesterdays is the complete guide to time travel in the world of Star Trek roleplaying. It covers everything from instrumentalities like the Guardian of Forever and the atavachron to techniques such as the slingshot effect and Borg temporal vortices to the rifts in spacetime which snare unwary travelers. Overlays and organizational details make members of the Department of Temporal Investigations, the 29th century Federation Timefleet, and other transtemporal characters ready to play.