Ok. Sorry for not providing exact err msg.

Now, here's the latest attempt.  Many thanks.

        // test output today's day extraction, divide milliseconds
       System.out.println("test date manipulation:" + (new
Date().getTime()) / (8640000));
                     // result: successful

                      // list files

                      File dir = new File("Temp");

                      String[] children = dir.list();
                      if (children == null) {
                          // Either dir does not exist or is not a
directory
                      } else {
                          for (int i = 0; i < children.length; i++) {
                              // Get filename of file or directory
                              String filename = children[i];
                              File fd = new File(filename);
                              long ftime = fd.lastModified();

                         // test output of the file day value
                               System.out.println(ftime);
                         // result: 0
                         // comment: bad
                         // question: what's wrong?

                             // System.out.println("now = " + new
Date().getTime());
                              /* debug */
                              // 1000 * 60 * 60 * 24 = 1 day = 8640000

       // System.out.println((new File(filename).lastModified()) /
(8640000));
                           /*
                     if ( (new Date().getTime()) / (8640000)  - (new
File(filename).lastModified()) / (8640000) ) > 30
{
                                      System.out.println("\nTemp files
older than 30 days: " + filename);
                             };
                              */
                          }

[...]

/* objective: list files in the Temp directory that are 30 days older
than today's date */

/* one way to solve the problem: compare today's date with each file's
dateTimeStamp */

// specifically, the technique to use here is to get today's date value
by
// using (new Date().getTime()) / (8640000));

// and another technique of using File Class's lastModified() method
// to get "similar" value for the date of each file
// this technique works with "known" file, see a case below.

          File fileD = new File("TestFile.txt");
          long fdate = fileD.lastModified();
          System.out.println("\t and it was last edited on " + fdate);

       // here's the clean code with Comments

                   // list files
                  // the Temp directory has 10 files, of which one
file name includes white spaces

                      File dir = new File("Temp");

                      String[] children = dir.list();
                      if (children == null) {

                      } else {
                          for (int i = 0; i < children.length; i++) {

                              String filename = children[i];
                              File fd = new File(filename);

                  // debug: to print out each file name
                  System.out.println(fd);
                  // result: yes it does

                              long ftime = fd.lastModified();
                  // test output of the file day value
                  System.out.println(ftime);
                  // result: 0
                  // comment: bad
                  // question: what's wrong?

                          }