Option 1:

 
  <meta name="date.created" content="YYYY-MM-DD"> (authored date)
  <meta name="date.available" content="YYYY-MM-DD"> (published date)
  <meta name="date.updated" content="YYYY-MM-DD; YYYY-MM-DD"> (date or dates that CONTENT was changed/updated)
  <meta name="date.modified" content="YYYY-MM-DD; YYYY-MM-DD"> (date or dates that HTML page was modified
                                                               in any way; e.g. html coding, encoding, styles,
                                                               or formatting changed,
                                                               but _content_ was not significantly changed.
                                                               May share the same date as 'date.updated' if both
                                                               content and formatting were changed at the same time.)

link: http://www.schemas-forum.org/registry/desire/element.php3?field=ID&value=dcq/date/modified 

   
  ["CONTENT", in parenthetical definitions above (_not_ in meta code) indicates words, sentences, images, 
     video, audio, or any other human communication format]<meta name="author" content="Author Name"> (content author. If this is the only 'author' tag, it should be assumed a single person
                                                                     wrote the content, created the style of the page, and published the page)
  <meta name="format_author" content="Author Name"> = "Web Author". 
                                       The person or persons who "html'ized" the document, only needed if
                                       a different person than the content author developed the document for web delivery.
  <meta name="format_designer" content="Author Name"> = Site Designer. 
                                     The person or persons (if different than persons above) who designed the style used on the page)

Option 2:


  <meta name="content_origin"  content="2005-04-02">
  <meta name="content_updated" content="2005-04-02">
  <meta name="minor_updates"   
         content="2005-04-02;
                  2005-05-09;
                  2009-09-21">

Option 3:

Abandon illogical, coder-designed HTML model.
Use logical, human readable, externally defined tags.
<revolutionary-concept>
Design computer systems and applications with enough intelligence
to parse and process variations created by humans.
(As opposed to trying to program humans to create code readable by computer systems.)
</revolutionary-concept>

Example:

<head>
 <meta>
    <meta-terms-defined-at>http://example.com/meta_defintions/</meta-terms-defined-at>

    <author>NAME</author>
    <date-created>YYYY-MM-DD</date-created>
    <date-available>YYYY-MM-DD</date-available>
    <date-updated>YYYY-MM-DD; YYYY-MM-DD</date-updated>
    <date-modified>YYYY-MM-DD; YYYY-MM-DD; YYYY-MM-DD</date-modified>
 </meta>
</head>

HOME | subindex a

Option Variation A:

Coding and the original HTML specifications created an environment where TAGs had to be single strings.

I say it's time we built a little intellegence into the parsers (as part of moving away from changing our own language to make the Programs happy).

All you need to do is make the parser recognize a space as part of the TAG.

This then allows for

<header>
  <metadata>
     <date created> .... </date created>
     <date available> .... </date available>
     <date updated> ... </date updated>
     <date modified> ... </date modified> 
  </metadata>
</header>