Are you referring to the last modification timestamp of the file or some internal data table?
If you are after the file timestamp, look into
Returns a timestamp for the date and time of the last modification of the file filename. If no filename is specified, the function will refer to the currently read table file.
filetime( 'xyz.xls' )
Will return the timestamp of the last modification of the file xyz.xls.
Load *, filetime() as X from abc.txt ;
Will return the date and time of the last modification of the file (abc.txt) as a timestamp in field X in each record read.
Returns the XML-header time stamp from a QVD file if any (otherwise NULL).
The filename is the name of a QVD file, if necessary including path.