I think that all time, from the beginning to the end, just is. It's like all the space between Land's End and John O'Groats. We can only see the part we are in, but the rest is still there.

So, if reincarnation is real there would be no limit to when you were born or which life you could live. I think every life is like a book. After death we might choose a particular life from any point in history, much like we might choose any book to read from a whole library.