I call existence as your "my-space" - it exists only NOW. I call existence as "actuality" - as the world constructed on the basis of action-observation
I add: There is no existence other than my existence. Nothing exists other than what I see as existing. This is the fundamental idea of the solipsism of action-observation.
Just as I cannot act-observe in the past or in the future but only NOW, so nobody else can act-observe on my behalf. I have to act-observe only by myself.
NOW is not only personal, it excludes the existence of others. There is no "common" world of observation, but there are as many unique worlds as there are Egos.
We seem to agree that individual solipsystems are temporally independent of one another and that "there are as many unique worlds as there are Egos." This is the point of view that I take in my theory of subjective time.
Re: temporal ordering and time travel:
Time flow is subjective and is always unidirectional. Time cannot logically flow backward. However, one can envision a scenario in which a mind perceives, say, 18th century spacetime points after perceiving 20th century spacetime points. Although this sequence of perceived spacetime points seems unconventional, the flow of time still remains unidirectional in this scenario. (The observer sees 18th century events after seeing 20th century events--and the flow remains "before -> after.")
We tend to think of the 20th century as existing after the 18th century; but I suggest that the 20th century is simply perceived subjectively as occurring after the 18th. Perhaps 18th century spacetime points can be perceived subjectively as occurring after 20th century ones.
We tend to believe that travel from the 20th to the 18th century is impossible. But our ideas regarding time travel and causality are rooted in the incorrect assumption that the "present" and the "flow of time" are objective phenomena. We need to be explicit that "time flow" and the "present" are subjective. And we should reconsider the possibility of time travel from this new perspective.