Views of Time: Eternalism, Presentism, Linear or Cyclical
1. The Eternalist View. The universe is viewed as a block in which past, present, and future are already just there. In this popular view, the Terminator can travel back and try to kill John Corner or Harry Porter can travel back and save Harry Porter!! Similarly, you can travel into future... or perhaps just see it?? Not that time-travel is possible, but this is the theoretical setup for such views.
2. The Presentist View. Time flows here. The universe is only the present which flees as soon as we can catch the present. The past and the future don't exist in the moment, though the past is fixed, and the future indefinite. Did you know that St. Augustine tried to locate the point in time where the universe is said to be present? Well, divisibility is infinite, so better not try it. No doubt, Kant called the grapes sour by taking refuge in idealism - time for his is just mental.
1. Linear Time: Time is a line that began somewhere in the past, is continuing in the present, and will end somewhere in the future.
2. Cyclical Time: Time is a cycle, and thus infinite. The Jains talk of Utsarpini (ascending arc) and Avasarpini (descending arc); the Hindus, of Sristi (Creation) and Pralaya (Dissolution).