The Uncertainty Principle In The Time Patrol Timeline

Poul Anderson's Time Patrol timeline is perhaps unique in sf and in our collective imagination. Let us consider four kinds of people who live in that timeline.

(i) The vast majority of people in this space-time continuum, at least before 19352 AD, neither travel through time nor know that any such travel occurs. Nor need they be concerned about it. If they are conscious that they are alive at their place and time, which they call here and now, then they are unaffected by the fact that, at some other place and time in the multi-dimensional cosmos, some time travellers regard their - the non-time-travellers' - timeline as having been deleted from existence or even as having been prevented from coming into existence. If their timeline had literally been prevented from coming into existence, then they would not be conscious here and now but they are conscious here and now...

(ii) After 19352 AD, populations, or at least some of them, know that time travel occurs, just as we know that space travel occurs, but they are neither directly involved in nor affected by it. Beyond that, people in category (ii) are in the same position as those in category (i).

(iii) Some people travel through time without ever experiencing causality violations or variable reality. They might as well be in a single continuous timeline like the one in Anderson's There Will Be Time.

(iv) However, every time traveller knows that, any time that he visits his "past," he might return to an altered "present." His options then become:

remain in the altered present;

return to the past to try to change events so as to restore the "original" or remembered present.

The Patrol is an agency for restoration. There is some uncertainty here. Manse Everard, having been informed of a temporal divergence in 1137 AD, travels to that year but to a point in time before the divergence. How does he then know that he is now in the timeline where the divergence will occur?