Timeline D is the fourth known timeline created as a direct result of The Time Traveler's temporal adventures. This timeline features an early 20th century consumed by war.
- 1880s-1890s - This timeline diverges from Timeline A when The Time Traveler and Nebogipfel arrive from the future aboard The Time Machine, and meet Moses. A Time Tank then also voyages back from the future and kidnaps the three. ("The Time Ships")
- Although the Time Traveler had already created timelines B and C by this point, Timeline D was a branch off the original timeline because the time traveler went back to a point before the other two timelines were created, and hence were all one timeline.
- Early 20th Century - World War I goes on for decades, ravaging Europe. London is covered in a massive dome to protect from the constant bombings. In desperation, the British discover the research left over by The Time Traveler and are able to duplicate his work, creating their own Time Tank, with which they travel back in time and retrieve The Time Traveler and his companions. These three then later escape in an experimental Time Car into the past, persued by the Time Tank, just as the London Dome is breached. This trip into the distant past leads to the creation of Timeline E. ("The Time Ships")