Only show Created and Modified dates if they have a value

templates/post.html

@@ -4,7 +4,7 @@
 <h1 class="title">
   {{ page.title }}
 </h1>
-<p class="subtitle"><strong>Created: {{ page.date }}</strong></p>
-<p class="subtitle"><strong>Modified: {{ page.updated }}</strong></p>
+{% if page.date %}<p class="subtitle"><strong>Created: {{ page.date }}</strong></p>{% endif %}
+{% if page.updated %}<p class="subtitle"><strong>Modified: {{ page.updated }}</strong></p>{% endif %}
 {{ page.content | safe }}
 {% endblock content %}