Hi Tony Walker, I have had several experiences of the time slip phenomena.
1) one night while living in Toronto, Canada, my partner and I both had the memories of an evening where we had lived two alternate realities. One event of the evening, as remembered the next morning, was that we entertained guests at a dinner party. The other event, a simultaneously memory of the same evening, we went out dancing.
2) the next occurrence was about 6 months later, at my work place. I worked in a wood working shop and I had four other co-workers. We were standing around chatting one morning during a coffee break… when I watched 2 of my co-workers wander off towards a cabinet that had been freshly built, and ready for delivery. One of the two picked up a long piece of wood and began striking the cabinet to inflict damage to it. After a minute or so they returned back to the group, where the foreman of our group suddenly exclaimed that there was damage to the new cabinet, and asked everyone how this could have happened. Nobody, but myself, had any memory of the incident.
3) I was once texted by my girlfriend while I was nearing her apartment towards the end of her work day, and she asked me to walk towards her work place, as she walked from work towards home. So that we could meet, and perhaps go out for dinner. While I was walking towards her, several blocks away, I had a day dream in the interval of a couple of steps on the pavement. I counted the cracks in the pavement, as I walked, there were 3 of them. Anyways, I imagined having missed my girlfriend as she walked on the opposite side of the street, where I then eventually back tracked to meet up with her realizing the mistake. In my day dream I had an imaginary argument with her about the incident, and during that argument I said all kinds of things that de-escalated the argument. This day dream occurred in the span of 3–4 paces, while I was walking. Then, do you know happened? I actually did miss her, as we walked past one another. I then doubled back and caught up with her. She then launched into an argument, and remembering the things I said in the day dream, I repeated them… and the argument was de-escalated just like in that day dream. The day dream was the equivalent of 40 minutes, and was a duplicate of the incident that happened in “real life.” I took me 3–4 steps to live out an incident that would occur subsequently in the near future. How weird is that?