[last_modified] not in <time> format

[schasoli]

[last_modified] output is not html standard
is: 11/04/2015
should: 2015-04-11
see https://html.spec.whatwg.org/multipage/infrastructure.html#valid-date-string

function shortcode_last_modified() {
return the_modified_date( 'd/m/Y', '', '', false );
return the_modified_date( 'Y-m-d', '', '', false );

It would be also nice to have a shortcode to get the date using the WP date format as set in settings.

[schasoli]

well, to stay as compatible as possible i added a new shortcode and tested
'last_modified_prefs' => array( $this, 'shortcode_last_modified_prefs' ),

changed
function shortcode_last_modified() {
/* return the_modified_date( 'd/m/Y', '', '', false );/
return the_modified_date( 'Y-m-d', '', '', false );
}
and added
function shortcode_last_modified_prefs() {
return the_modified_date('','','',false);
}

works fine for me.

[sheabunge]

Perhaps a good middle ground would be to include the standard YYYY-MM-DD format inside the datetime attribute on the <time> element, and then use the preferences format to display the date on the page. Something like this:

<time datetime="2015-04-21">21 April 2014</time>

[schasoli]

w3c validator accepts it and pubdate is not used anymore. So I think yours is the best solution for a footer. I do it like this
$date1 = the_modified_date( 'Y-m-d', '', '', false );
return the_modified_date('','<time datetime="'.$date1.'">','</time>',false);

looking at http://html5doctor.com/time-and-data-element/ maybe this would be nice for google and co:
<article itemscope itemtype="http://schema.org/BlogPosting">
…
<data itemprop="datePublished" value="2015-04-21">21 April 2014</data></article>
But it would need to more shortcodes:
beginArticle, endArticel or so.
edit: https://wordpress.org/plugins/itempropwp/ could be used for this

[sheabunge]

I've updated the code to use the first format. I'm not entirely sure about using the second method; it looks more suited to a local article footer such as the area where categories, tags, published date, etc are displayed, not a global footer area which could be virtually anywhere.