Having been a member of the SOC for many years, Time Movement or Time Travel as it has been labeled has been illegal for 21 years now. The last Time Travel mission was 23 years ago and was the 5th and last attempt of a History "Reset". Like the 4 times before it, it was an utter failure at the attempt to restore the Original Timeline (OT).
There is only one known way to Time Travel, which is not to say there isn't the possibility of others, but for it to be possible, many unique things would have to occur. The first experience of Time Travel happened in 1974 completely by accident when the first SOC Ship was able to complete an Interstellar Space Flight by Folding Space and thus the side effect was a Time Movement as well. The first Time Movement did not affect History in any way, but the 2nd one, which happened when the Ship returned to Earth’s Orbit, did.
Other than that, there is NO Other Documented or Detected Time Movements from anyone else on Earth. Stories you hear of Time Travelers simply are not true. People like this John Titor are Fake. I checked his name against the SOC database and his is not a Member of the SOC. Time Movements are virtually impossible to complete on Earth. There are theories for it, but no practical or successful experimentation. Even the DARPA group shelved their Time Movement or Travel Program after many failures. You just cannot create the needed conditions on Earth for Time Movements. Even if you could, the chances of creating another Timeline that would make things worse than they currently are is too easy and too great. It's believed that you don't even have to have any sort of interaction with people of the past to create a new Timeline that the "Ripples" created by Time Movements themselves do that. In that respect and from actual incidents, it surely does appear to be the affirmative.