diff --git a/sitemap.xml b/sitemap.xml
index bed1a19..e59d8be 100644
--- a/sitemap.xml
+++ b/sitemap.xml
@@ -10,14 +10,14 @@ layout: nil
     {% for post in site.posts %}
     <url>
         <loc>{{ site.url }}{{ post.url }}</loc>
-        <lastmod>{% if post.modified %}{{ post.modified | to_xmlschema }}{% else %}{{ post.date | to_xmlschema }}{% endif %}</lastmod>       
+        <lastmod>{% if post.modified %}{{ post.modified | date_to_xmlschema }}{% else %}{{ post.date | date_to_xmlschema }}{% endif %}</lastmod>       
     </url>
     {% endfor %}
     
     {% for page in site.pages %}
     <url>
         <loc>{{ site.url }}{{ page.url }}</loc>
-        <lastmod>{{ site.time | to_xmlschema }}</lastmod>
+        <lastmod>{{ site.time | date_to_xmlschema }}</lastmod>
     </url>
     {% endfor %}
 </urlset>
\ No newline at end of file