It follows logically from Einstein's 1905 postulates that, if two clocks are in relative motion, either clock is slow as judged from the other clock's system (SYMMETRIC time dilation). An obvious implication is that

time SPEEDS UP for any traveler.

That is, any traveler who checks stationary clocks against his spaceship's clocks will find stationary clocks slow and his spaceship's clocks FAST. This also means that the traveler sees himself aging FASTER than stationary people.

This is the valid deduction from Einstein's postulates but it is sterile in terms of predictions (if Einstein had obeyed logic in 1905, his special relativity would not have survived). So high priests in the Einstein cult fraudulently teach that

time SLOWS DOWN for the traveler:

Brian Greene: https://youtu.be/Q1y3YnPgaY4?t=1157

Albert Einstein 1911: "The clock runs slower if it is in uniform motion..." http://einsteinpapers.press.princeto...vol3-trans/368

Richard Feynman: "Now if all moving clocks run slower, if no way of measuring time gives anything but a slower rate, we shall just have to say, in a certain sense, that time itself appears to be slower in a space ship." http://www.feynmanlectures.caltech.edu/I_15.html

Brian Greene: "If you're moving relative to somebody else, time for you slows down." https://m.youtube.com/watch?v=QnmnLmwBmfE

Neil deGrasse Tyson: "...Einstein's special theory of relativity, which gives the precise prescription for how time would slow down for you if you are set into motion." http://abcnews.go.com/Entertainment/...ry?id=32191481

Jim Al-Khalili: "Einstein showed that for anything (or anyone) travelling at speeds approaching that of light...time literally runs more slowly." https://scienceinschool.org/2009/issue11/timetravel

More he https://twitter.com/pentcho_valev

Pentcho Valev