Some shifters may shift from this reality to the future or past. And, there are people who have already returned to the past and continue to live until they reach the present.
Time essentially does not exist, and it is a kind of side effect that existence/consciousness experiences as it passes the frame to the next scene. And, in the case of a shared reality, each being/consciousness precisely emulates each other's avatars and personalities, creating an optical illusion as if they are interacting together. And although each being/consciousness appears to be in the same time zone and the same reality, in reality, the time zone is different and the realities are slightly different. These minor differences can be seen in the stories of people with different memories due to the Mandela effect.
So, going back to the beginning, if you were to experience another alternate reality and come back to this one, nothing would change. However, other consciousnesses/beings who share this common reality will continue to experience moving to the next time frame while you experience other alternate realities.
So, it is said that extraterrestrial races of 4th density or higher, who can freely change reality, freely choose their own time zone for a certain time range, such as 10 years, and then move on to the next 10-year range.
Think of this reality as a VR game, and think of time as a sort of selectable theme. It will be easier to understand if you think of it as a theme such as ancient, medieval, and modern times. And, imagine having your avatar accurately simulated and reflected in your own reality. Then, we can solve the problem of time travel.