From a HIGHER point of view, all of time has already happened. You can view it as a movie reel. You can look at any point in time. It is all there at once.
However, all the points are changing as humans live their lives.
From a middle point of view, a being often reincarnates into their own family. Grandpa becomes grandson. And so, they see themselves in the lives they have lived, in a string.
However, this same being may also be incarnating in several other times, like the past, or the future, at the same time. And so, that part of him may be reincarnating in that family, but at a different time. (using the Gregorian calendar)
And of course, you have humans, at this time and place being fully immersed in time. And we generally experience it as linear.