What is the convention of the last line (or footer) of a manpage

Question

I want to know where I can find documentation on the meaning or convention of the last line of a manpage, looking through manpage for man didn't help. For example:

…$ man top|tail -n 1
procps-ng                       July 2014                          TOP(1)

…$ man rm|tail -n 1
GNU coreutils 8.25               February 2017                           RM(1)

Regarding the TOP command:

• procps-ng: Is this a module or family of tools the top command belongs to?
• July 2014: Is this the date the documentation was written or the date of the release of this version of top?
• TOP(1): I'm guessing this is a self reference to the manpage itself.

Answer 1

Assuming it was generated using GNU tools on Linux, both the header and the footer are specified together as arguments to the .TH macro. From man 7 groff_man:

.TH title section
   [footer-middle] [footer-outside] [header-middle] Define the
  title of the man page as title and the section as section.
  See man(1) for details on the section numbers and suffixes
  applicable to your system.  title and section are positioned
  together at the left and right in the header line (with
  section in parentheses immediately appended to title).
  footer-middle is centered in the footer line.  footer-outside
  is positioned at the left in the footer line (or at the left
  on even pages and at the right on odd pages if double-sided
  printing is active).  header-middle is centered in the header
  line.  If section is a simple integer between 1 and 9
  (inclusive), or is exactly “3p”, there is no need to specify
  header-middle; the macro package will supply text for it.

And the rest of the convention is given in man 7 man-pages:

Title line
   The first command in a man page should be a TH command:

          .TH title section date source manual

   where:
          title     The title of the man page, written in all caps
                    (e.g., MAN-PAGES).

          section   The section number in which the man page should be
                    placed (e.g., 7).

          date      The date of the last nontrivial change that was made
                    to the man page.  (Within the man-pages project, the
                    necessary updates to these timestamps are handled
                    automatically by scripts, so there is no need to
                    manually update them as part of a patch.)  Dates
                    should be written in the form YYYY-MM-DD.

          source    The source of the command, function, or system call.

                    For those few man-pages pages in Sections 1 and 8,
                    probably you just want to write GNU.

                    For system calls, just write Linux.  (An earlier
                    practice was to write the version number of the
                    kernel from which the manual page was being
                    written/checked.  However, this was never done
                    consistently, and so was probably worse than
                    including no version number.  Henceforth, avoid
                    including a version number.)

                    For library calls that are part of glibc or one of
                    the other common GNU libraries, just use GNU C
                    Library, GNU, or an empty string.

                    For Section 4 pages, use Linux.

                    In cases of doubt, just write Linux, or GNU.

          manual    The title of the manual (e.g., for Section 2 and 3
                    pages in the man-pages package, use Linux
                    Programmer's Manual).