Technically, these disagreements occur when the spacetime interval between the events is 'space-like', meaning that neither event lies in the future light cone of the other.
If one of the two events represents the sending of a signal from one location and the second event represents the reception of the same signal at another location, then as long as the signal is moving at the speed of light or slower, the mathematics of simultaneity ensures that all reference frames agree that the transmission-event happened before the reception-event.
In technical papers, physicists generally avoid the commonplace language of "moving" or "traveling" through time.
Like forward time travel, backward time travel has an uncertain origin.
Samuel Madden's Memoirs of the Twentieth Century (1733) is a series of letters from British ambassadors in 19 to diplomats in the past, conveying the political and religious conditions of the future.
However, the story never makes it clear whether these events are real or a dream.
as the protagonist, Ebenezer Scrooge, is transported to Christmases past and future.
Time travel is the concept of movement (such as by a human) between certain points in time, analogous to movement between different points in space, typically using a hypothetical device known as a time machine, in the form of a vehicle or of a portal connecting distant points in time.