Two conditions are required to give rise to its illusion: motion (or change, or difference) and memory.
If an object were not to change, if it remained absolutely the same, if it didn't move, grow, age, or crumble in any way (and if you as the observer remained constant too) one would not feel the passage of time. (And is that not the truth: atoms never age. (They do not show the wear and tear of billions of years.)
In addition, you would need a sense of memory to sense the passage of time. Memory compares the current situation with that of the past. Therefore, if all that you perceived consisted of the present, then time as a concept could not arise either
When you flip through a series of stills, such as what occurs when you screen a strip of film, then time will seem to pass. But it does so only because each still is a little different from the one before, plus the fact that you retain the image in your short-term visual memory. Therefore, I propose that time is a human artifact, the illusion you get when you flip rapidly through a set of slivers.
Roll 'em!
