CTAN has a new package: getfiledate
The package fetches from the system the date of last modification or opening of a resident file. It is based on an idea by Heiko Oberdiek that appeared in February 2009 on the TeX newsgroup website comp.text.tex, ie, using the \pdffilemoddate command of pdfTeX. A user- friendly interface is provided for obtaining and presenting the needed filedate in several formats.
This package is located at http://tug.ctan.org/tex-archive/macros/latex/contrib/getfiledate . More information is at http://tug.ctan.org/pkg/getfiledate (if the package is new it may take a day for that information to appear). We are supported by the TeX Users Group http://www.tug.org . Please join a users group; see http://www.tug.org/usergroups.html .
getfiledate – Find the date of last modification of a file
The package fetches from the system the date of last modification or opening of an existing file, using the function \pdffilemoddate (present in recent versions of pdfTeX); the user may specify how the date is to be presented.