Ok, here's an interesting thought experiment:
You're sitting at a table. At exactly 11am, a note appears in front of you saying "At exactly 12pm (one hour from now), send this note back in time exactly one hour"
So, you do that at exactly 12pm.
(1) Who wrote the note?
(2) How old is the note?
(1) I have no way of knowing. The realm of what's possible in this universe isn't well enough defined to rule anyone or anything out. No one is a possibility as well.
(2) Age is relative to timeline. Given that the note only ever exists in the narrative you present:
With regard to the timeline that we typically speak in terms of when we use terms such as "11am" and "12pm", the note is brand new at 11am and progresses like any other object from there, until 12pm, at which point it hits one hour old and ceases to exist.
On the other hand, with regard to a hypothetical timeline that the note follows with its own time dimension (such that successive 11ams on this day exist*), the question of age would become meaningless unless and until a starting point could be identified. Naturally, if such a starting point
were identified, the note's age according to this timeline would be such that:
- given c, defined as the number of 11am-12pm cycles the note has gone through, and
- given t, defined as the current time
Age = c hrs + (t - 11 hrs)
* Such a timeline could be graphed to look something like this:
///////////////////////////////////////////////////////////////// (and so on)
where the y-axis represents the timeline we typically think in with a range of one hour spanning from 11am to 12pm, and where the x-axis represents another time dimension, needed to allow for multiple points with the same y-coordinates.