Add message on old posts

source/_layouts/post.html.twig

@@ -25,6 +25,15 @@
     {% include 'post/intro-image' %}
 
     <div class="content mb-6">
+        {% set limit = 'now'|date_modify('-12 months')|date('U') %}
+        {% if page.date|date('U') < limit %}
+            <div class="border-2 border-blue p-4 mb-4">
+                <p class="mb-0">
+                    <span class="font-bold">Warning:</span> This post is over a year old. I don't always update old posts with new information, so some of this information may be out of date.
+                </p>
+            </div>
+        {% endif %}
+
         {% block excerpt %}{% endblock %}
         {% block content %}{% endblock %}
     </div>