layouts fix: use date_to_xmlschema in schema.org's itemprop

_layouts/single.html

@@ -24,8 +24,8 @@ layout: default
   <article class="page" itemscope itemtype="https://schema.org/CreativeWork">
     {% if page.title %}<meta itemprop="headline" content="{{ page.title | markdownify | strip_html | strip_newlines | escape_once }}">{% endif %}
     {% if page.excerpt %}<meta itemprop="description" content="{{ page.excerpt | markdownify | strip_html | strip_newlines | escape_once }}">{% endif %}
-    {% if page.date %}<meta itemprop="datePublished" content="{{ page.date | date: "%B %d, %Y" }}">{% endif %}
-    {% if page.last_modified_at %}<meta itemprop="dateModified" content="{{ page.last_modified_at | date: "%B %d, %Y" }}">{% endif %}
+    {% if page.date %}<meta itemprop="datePublished" content="{{ page.date | date: date_to_xmlschema }}">{% endif %}
+    {% if page.last_modified_at %}<meta itemprop="dateModified" content="{{ page.last_modified_at | date: date_to_xmlschema }}">{% endif %}
 
     <div class="page__inner-wrap">
       {% unless page.header.type == 'overlay' or page.header.type == 'default' %}

_layouts/splash.html

@@ -12,8 +12,8 @@ layout: default
   <article class="splash" itemscope itemtype="https://schema.org/CreativeWork">
     {% if page.title %}<meta itemprop="headline" content="{{ page.title | markdownify | strip_html | strip_newlines | escape_once }}">{% endif %}
     {% if page.excerpt %}<meta itemprop="description" content="{{ page.excerpt | markdownify | strip_html | strip_newlines | escape_once }}">{% endif %}
-    {% if page.date %}<meta itemprop="datePublished" content="{{ page.date | date: "%B %d, %Y" }}">{% endif %}
-    {% if page.last_modified_at %}<meta itemprop="dateModified" content="{{ page.last_modified_at | date: "%B %d, %Y" }}">{% endif %}
+    {% if page.date %}<meta itemprop="datePublished" content="{{ page.date | date: date_to_xmlschema %d, %Y" }}">{% endif %}
+    {% if page.last_modified_at %}<meta itemprop="dateModified" content="{{ page.last_modified_at | date: date_to_xmlschema %d, %Y" }}">{% endif %}
 
     <section class="page__content" itemprop="text">
       {{ content }}