Generally, fax servers which "dump" faxes onto your desktop or folder, do so by naming it with date and time:
For instance, mine comes in:
FAX-372011 20220 PM_1.pdf meaning
it's a fax:
that arrived on March 7, 2011 @ 2:02:20 pm. Just in case two pdfs arrive within one second of each other, a 1 is placed at the end.
