(Bolded words are revised.)
In the world of science, you would need a machine that moves faster than the speed of light to travel through time. But you involuntarily move through this dimension every day.
You may regard the past as cemented, but it is always changing. Let’s say you have a lot of work to do. You might reminisce longingly about being in grade school, when you were free to take time for granted. But if you revisit that same moment on a different day, your naiveté might appear as a limitation.
Your memory will always refine particular moments and blur others, and its multiple realities are as infinite as the parallel universes that exist in theoretical physics.