Before discussing multi-linear time, one must establish what the concept of time is. Time, for this argument, is a tool that measures the cycles of day and night. It can be divided into decreasing discrete measurements (hours, minutes, seconds). A collection of discrete measurements can represent a block (day) or several blocks (week, month, year). This is an universal truth, but not a law. Our concept of time is not necessarily the same for another species, but time occurs. To borrow from the incompleteness theorem of Gödel, truth is not a function of logic.
Our concept of time is that seconds lead to minutes to hours to days to weeks to years. This is linear time or simply A to B. Hawking when writing on the concept of worm holes noted that the truth that the shortest distance between two points is a straight line, especially when two points are folded over. Take a piece of paper and make two points on it. Fold the paper so the points are over each other, and that is what Hawking meant.
In our concept of time, the War of 1812 started on Friday, June 18th, 1812. It is a definite dot on the timeline. Common theories on time travel would say we could build a device and go back in time to June 18th, 1812. The issue is going forward in time.
To be able to go forwards in time, say to March 1st, 3500, all time must have happened. Clarifying to travel forwards in time, all time, from the beginning of the universe to the end of it, must have already occurred. Traveling forward in time would have a dead-end. And again this is linear time as we know it.
The concept of multi-linear time is that all time that has/will ever occur happens along the straight line of our seven day week. Every single Friday in all of history happens on Friday; first Friday and final Friday occurs all at once. One p.m Friday now is one p.m. Friday throughout all of history. Basically time is L-shaped with the days of the week moving left to right and years and its more discrete parts from bottom to top. Why would this be superior to our standard concept of time? The points on the line are still the same.
Then we come back around to Hawking's concept of a worm hole. Nimtz and Stahlhofen claim to have succeeded with quantum tunneling which is theoretically similar to Hawking. In linear time, folding time from say Monday, February 28th, 2011 to Friday, June 18th, 1812 would not be possible because it is not a folding of time, but a fold and twist. In multi-linear time, you could fold Friday, whatever year, over to Friday, June 18th, 1812.
Following Baye's Theorem [P(H/E)=P(E/H)xP(H)/P(E), where H=hypothesis and E=evidence supporting H] the probability of time travel in the current concept of linear time is decidedly less probable than in a multi-linear concept. Not a perfect hypothesis, but closer to an universal truth than what is commonly accepted.