Look at the time on your computer, and look at the timestamp of your file.

There are all sorts of reason which could lead to a file's timestamp to be more recent than what your computer thinks is the current time.

From: Shiyuan <gshy2014@gmail.com>
To: help-gnu-emacs@gnu.org
Sent: Wednesday, October 12, 2011 11:31:00 AM
Subject: file changed prompt

Hi,
My emacs keeps prompting "file on disk changed". But actually it's not. What could cause this problem?
Thanks

Shiyuan