I watched the movie Somewhere in Time last night. It's an interesting film because of the time travel aspect. In the film the protagonist travels back in time and to do this he hypnotizes himself to believe he is in the year 1912. To make this work, he has to remove everything from the room that would remind him of the modern era. He also dresses himself in clothes from that time period, that would fit in where he is going. He then hypnotizes himself and ends up traveling back in time. It's an interesting idea for a technique. In the movie he had a specific day and time he was showing up. What ends up bringing him back is an encounter with something modern.
Could this be used as a technique for retroactive magic or for space/time magic work in general? I don't see why it couldn't be. If you were going to use this for retroactive magic, you'd need to acquire period technology, clothing etc. This would help your mind accept the idea that you were traveling back into the past.
Applying this technique to the future would be harder, as obviously you wouldn't have access to period clothing or technology. Nonetheless I don't think it's impossible. It really comes down to questioning if you even need a label of the future to access a different point of time. And if you are concerned about that, the way you could get around this is to use the technique to contact your future self or a future descendent, to provide you a repository for your consciousness.
What makes this technique so interesting is that hypnosis is used to achieve an altered state of awareness that accepts the possibility of being in another time (although in the case of the movie, anchored to the same space). The anchoring of the space provides stability for the mind, in terms of accepting the temporal shift, but still having a space the mind is familiar with. I've used hypnosis enough to know it can be useful for hitting heavily altered states of awareness, including temporal shifts, so I think it's possible to experiment with a concept such as this and use it with some degree of success for making changes to your past or future.
You'd need to develop a script that you could use to put your mind into a deep state of relaxation while also pointing it to a specific temporal moment you want it to inhabit. It also helps if you can describe the spatial aspects in some detail, in order to provide a grounding in the new environment you want your mind to go to. Most of all though you have to want to go there. It has to be somewhen that you want to be more than anywhere else.
My own experiences with retroactive magic have involved going back to a past version of myself and then helping the version make a different choice. I've found it useful to thoroughly explore the memory setting of that past version in order to fully integrate my present self into that post moment, but I've also used my past version as my anchor point. That past version has also provided that emotional basis for needing to be in the past. In the movie, since the character was going into a past where he didn't yet exist, the emotional basis that caused him to need to be there was his desire to meet someone in the past that he felt an attachment to. We can't ever underestimate the power of desire and emotion and where and when it can take us.