Watching a download in progress I did:

$ ls -latr | tail
-rw-r--r--  1 # #    97171 Jul  5 12:44 DocumentView857d.pdf
-rw-r--r--  1 # #    55728 Jul  5 12:44 index6e5c.html.tmp
-rw-r--r--  1 # #  6783785 Jul  5 12:45 DocumentViewb358.pdf
-rw-r--r--  1 # #    55504 Jul  5 12:45 indexd457.html.tmp
-rw-r--r--  1 # #    55504 Jul  5 12:46 indexfd99.html.tmp
drwxr-xr-x  9 # #    81920 Jul  5 13:03 .
-rw-r--r--  1 # # 17084416 Jul  5 13:11 DocumentView637d.pdf
-rw-r--r--  1 # #  9281536 Jul  5 13:11 DocumentViewb764.pdf
-rw-r--r--  1 # # 10375168 Jul  5 13:11 DocumentViewbc4f.doc
-rw-r--r--  1 # #  2822144 Jul  5 13:11 DocumentView710a.pdf

About 5 minutes later I did it again:

$ ls -latr | tail
-rw-r--r--  1 # #    55728 Jul  5 12:44 index6e5c.html.tmp
-rw-r--r--  1 # #    55504 Jul  5 12:45 indexd457.html.tmp
-rw-r--r--  1 # #  6783785 Jul  5 12:45 DocumentViewb358.pdf
-rw-r--r--  1 # #    55504 Jul  5 12:46 indexfd99.html.tmp
-rw-r--r--  1 # #  4351415 Jul  5 13:03 DocumentView710a.pdf
drwxr-xr-x  9 # #    81920 Jul  5 13:15 .
-rw-r--r--  1 # # 18980864 Jul  5 13:16 DocumentView637d.pdf
-rw-r--r--  1 # # 11177984 Jul  5 13:16 DocumentViewb764.pdf
-rw-r--r--  1 # #   360448 Jul  5 13:16 DocumentView5ecf.pdf
-rw-r--r--  1 # # 12271616 Jul  5 13:16 DocumentViewbc4f.doc

Why would the timestamp on DocumentView710a.pdf
go backwards from 13:11 to 13:03?