The %%mtime macro expands to last modification time of
the source document. It is useful to register when the file was last
changed. This macro is a "sister" of the
%%date macro, so it accepts exactly the same formatting directives.
As an example, this User Guide source file was last edited on Fri
Dec 4 15:44:11 2009. This date was expanded from %%mtime(%c)
.