diff --git a/.eleventy.js b/.eleventy.js
index b387b3c..9d6487d 100644
--- a/.eleventy.js
+++ b/.eleventy.js
@@ -12,6 +12,11 @@ module.exports = function(eleventyConfig) {
     return DateTime.fromJSDate(dateObj).toFormat("dd LLL yyyy");
   });
 
+  // https://html.spec.whatwg.org/multipage/common-microsyntaxes.html#valid-date-string
+  eleventyConfig.addFilter('htmlDateString', (dateObj) => {
+    return DateTime.fromJSDate(dateObj).toFormat('yyyy-LL-dd');
+  });
+
   // only content in the `posts/` directory
   eleventyConfig.addCollection("posts", function(collection) {
     return collection.getAllSorted().filter(function(item) {
diff --git a/404.md b/404.md
index a5465e4..c3d1080 100644
--- a/404.md
+++ b/404.md
@@ -1,6 +1,7 @@
 ---
 layout: layouts/home.njk
 permalink: 404.html
+excludeFromSitemap: true
 ---
 # Content not found.
 
diff --git a/feed/feed.njk b/feed/feed.njk
index 636c9c2..f889671 100644
--- a/feed/feed.njk
+++ b/feed/feed.njk
@@ -1,5 +1,6 @@
 ---
 permalink: feed/feed.xml
+excludeFromSitemap: true
 ---
 <?xml version="1.0" encoding="utf-8"?>
 <feed xmlns="http://www.w3.org/2005/Atom">
@@ -23,4 +24,4 @@ permalink: feed/feed.xml
 		<content type="html">{{ post.templateContent | htmlToAbsoluteUrls(absolutePostUrl) }}</content>
 	</entry>
 	{%- endfor %}
-</feed>
\ No newline at end of file
+</feed>
diff --git a/feed/htaccess.njk b/feed/htaccess.njk
index 3318d60..8b4e0d9 100644
--- a/feed/htaccess.njk
+++ b/feed/htaccess.njk
@@ -1,5 +1,6 @@
 ---
 permalink: feed/.htaccess
+excludeFromSitemap: true
 ---
 # For Apache, to show `{{ metadata.feed.filename }}` when browsing to directory /feed/ (hide the file!)
-DirectoryIndex {{ metadata.feed.filename }}
\ No newline at end of file
+DirectoryIndex {{ metadata.feed.filename }}
diff --git a/sitemap.xml.njk b/sitemap.xml.njk
new file mode 100644
index 0000000..d1745a3
--- /dev/null
+++ b/sitemap.xml.njk
@@ -0,0 +1,16 @@
+---
+permalink: /sitemap.xml
+excludeFromSitemap: true
+---
+<?xml version="1.0" encoding="utf-8"?>
+<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
+{%- for page in collections.all %}
+{%- if not page.data.excludeFromSitemap %}
+  {% set absoluteUrl %}{{ page.url | url | absoluteUrl(metadata.url) }}{% endset %}
+  <url>
+    <loc>{{ absoluteUrl }}</loc>
+    <lastmod>{{ page.date | htmlDateString }}</lastmod>
+  </url>
+{%- endif %}
+{%- endfor %}
+</urlset>