Time travel is a mystery we cannot explain fully to you. This is not dependent on our wishes, or your desire, but on the rules we must follow. These rules are above the Council of Worlds. These rules are not negotiable. However, we can give you some sense of what is going on. Beyond this, there is not much we can say until you reach 4th Density.
Time is linear only in your mind. It is not what it seems. Your sense that time is linear in the Universe is supported by what you observe: clocks running in seeming syncronicity; planetary movements that are predictable; testimony of other people you interact with to the effect that they, too, observe the same time passage as you do. However, time is only a factor, and as such when put into mathematical calculations can be affected along with the other factors. The Universe is such a huge mathematical calculation. In the portion of the world that you live in, the factors are stable enough that the time factor never varies enough to be noticed. This makes you think that time is a fixed factor. It is not fixed. We understand what other factors are involved, and how to modify them so that the time factor changes as we wish.
The issue of time travel is confusing to humans, who see the movies where parties go into the future as well as the past. Would that not be the case, as if one can go in one direction, why not the other? One cannot travel into the future, except in small increments, hours at most. Leaping into the future is a fiction. One can travel into the past, as that is a trail marked in the substance of the Universe, strands that can be unwoven and rewoven, a rope that stretches back endlessly. The past has markers. Grip points. It has been built, where the future has not yet been built. A phrase much in use is the Time/Space Continuum. This is simply a way of stating that matter may be in a different place, or space, depending on the time, and that matter leaves a trail, or continuum, over time. You can equate the Time/Space Continuum to our term strands, being woven and unwoven, which we consider more exact as it refers to the webbing that takes place.
What would happen if one went back along a particular strand, unraveling it, and changed the circumstances surrounding the strand. Would it change the present, and thus the future? Yes, but not to the degree depicted in the movies, where people wink out like lights and buildings disappear from sight and even from the memory of all. How could it, as each of these occurrences is composed of numerous strands, weaving in multiple directions, and it is impossible to change them all. What in fact occurs, should one be allowed to go back in time and make an alteration, is that the future is essentially unchanged. We say essentially, as there has been change, but due to the interweaving of other strands, this is muted. The Council of Worlds strictly administers time travel, as should one go back in time and really work at it, changes would begin to appear.
An example might be a child, born with a genetic defect. Should one go into the strands leading to conception, and change the DNA strands affecting the defect, the child would be born whole. However, each second that ticks past the moment of conception complicates this, as the webbing of strands has begun. At three months the fetus has strands of interplay with the mother's host womb, her blood and DNA makeup, such that simply changing the makeup of the genetics of the fetus is not enough. A panoply has been set in motion, and defectiveness to some degree will still present at birth. At three months, to effect a cure, one must also delve into the strands that weave into the mother's system, the womb, even out into the environs surrounding mother and child. It's all quite complicated. So if this is the case, why would the Council of Worlds bother to watchdog time travel? Where changes are subtle, they can effect the overall when done systematically. As intense as agendas are, masters over minions could set them about a never ending routine that would affect what has been written, trip the balance enough to be worthwhile to the master.
Is not one moment another's future and yet another's past? If we today travel back, would we not be deemed visitors from the future? And in this context, if the Earth were to hypothetically receive visitors claiming to be from the future, would that not mean that we are not the present at all, and that the future, for us, has therefore been written? This confusion can be settled if one understands that the Earth is not having visitors from the future, no matter how this may have been stated. Misunderstandings occur during genuine channeling sessions, and an example of what will be more prevalent in the future can be misunderstood to be an actual visitor from the future. The future has not been written. You are writing it now, moment by moment, decision by decision. When travel back through time occurs this is not recorded in the memory of nonparticipants, only in the memory of the travelers. Pains are taken to ensure that this be so. Travel back in time is done for such matters as capturing genetic material long lost, for instance, not to distort or pollute a memory.
Future travel is done only to coordinate activities of contactees and ourselves, where one has to be, as you say, in two places at once. This is not done casually, and in all cases for the procedure to be applied to a particular contactee or alien visiting Earth, the Council of Worlds must give its approval. This means that one contactee must experience missing time, but another may be jumped forward in time for a conference and then returned. Their subconscious records the memory as lineal, a fuller day. This is done on a person by person basis, so that for some countactees, involved in what is deemed crucial activities having a great impact on the Transformation, permission is granted. The same logic applies to ourselves, who are held under stricter rules. There are no Zetas in the Service-to-Others, in your Solar System, who currently are allowed to be in two places at once by inching forward in time. How is this future step done? The strands, in their current momentum and direction, are accelerated for that individual contactee, and then unwoven again. The entity, who is not affected by this weaving and unweaving, remembers, and speaks to the subconscious later, building a memory of the encounter.