The conversion of "local time" into "time" was illegitimate - the moving clock became slow and the stationary one FAST, which did not follow validly from Einstein's 1905 postulates. Travel into the future became possible, science died and was replaced by magic:
http://www.bourbaphy.fr/damourtemps.pdf
Thibault Damour: "Textbook presentations of Special Relativity often fail to convey the revolutionary nature, with respect to the "common conception of time", of the seminal paper of Einstein in June 1905. It is true that many of the equations, and mathematical considerations, of this paper were also contained in a 1904 paper of Lorentz, and in two papers of Poincare submitted in June and July 1905. It is also true that the central informational core of a physical theory is defined by its fundamental equations, and that for some theories (notably Quantum Mechanics) the fundamental equations were discovered before their physical interpretation. However, in the case of Special Relativity, the egregious merit of Einstein was, apart from his new mathematical results and his new physical predictions (notably about the comparison of the readings of clocks which have moved with respect to each other) the conceptual breakthrough that the rescaled "local time" variable t' of Lorentz was "purely and simply, the time", as experienced by a moving observer. This new conceptualization of time implied a deep upheaval of the common conception of time. Max Planck immediately realized this and said, later, that Einstein's breakthrough exceeded in audacity everything that had been accomplished so far in speculative science, and that the idea of non-Euclidean geometries was, by comparison, mere "child's play". [...] The paradigm of the special relativistic upheaval of the usual concept of time is the twin paradox. Let us emphasize that this striking example of time dilation proves that time travel (towards the future) is possible. As a gedanken experiment (if we neglect practicalities such as the technology needed for reaching velocities comparable to the velocity of light, the cost of the fuel and the capacity of the traveller to sustain high accelerations), it shows that a sentient being can jump, "within a minute" (of his experienced time) arbitrarily far in the future, say sixty million years ahead, and see, and be part of, what (will) happen then on Earth. This is a clear way of realizing that the future "already exists" (as we can experience it "in a minute")."
Pentcho Valev