fix date stuff

_includes/layouts/post.njk

@@ -4,7 +4,7 @@ layout: page.njk
 
 <p>Written by {{ author }}</p>
 
-<p>Posted on <time datetime="{{ date-posted }}">{{ date-posted | htmlDateString }}</time></p>
+<p>Posted on <time datetime="{{ datePosted }}">{{ date-posted | htmlDateString }}</time></p>
 <p>Updated on <time datetime="{{ date-updated }}">{{ date-updated | htmlDateString }}</time></p>
 
 <img src="{{ image.src }}" alt="{{ image.alt }}">