diff --git a/layouts/blogpost.erb b/layouts/blogpost.erb
index 0c4253c..fedb926 100644
--- a/layouts/blogpost.erb
+++ b/layouts/blogpost.erb
@@ -9,7 +9,7 @@
 <meta name="twitter:label1" value="Author" />
 <meta name="twitter:data1" value="<%= @item[:author] %>" />
 <meta name="twitter:label2" value="Created at" />
-<meta name="twitter:data2" value="<%= @item[:created_at] %>" />
+<meta name="twitter:data2" value="<%= gitmtime  %>" />
 <meta name="twitter:card" content="summary_large_image" />
 
 <!-- Animate.css -->
@@ -31,7 +31,8 @@
     <% end %>
     <div class="details animated fadeInRight">
       <small>
-        Geschreven op <%= item[:created_at] %><br>
+        Geschreven op <%= gitctime %><br>
+        Laatst aangepast op <%= gitmtime %><br>
         Leestijd: <%= reading_time @item %>
       </small>
     </div>
diff --git a/lib/helpers/blog.rb b/lib/helpers/blog.rb
index 96db131..55b932b 100644
--- a/lib/helpers/blog.rb
+++ b/lib/helpers/blog.rb
@@ -25,4 +25,20 @@ module BlogHelper
       </figure>
     HTML
   end
+
+  def gitctime
+    # find file last modification time
+    filepath=@item[:content_filename]
+    str=`git log --format=%cd --date=short -- #{filepath} | tail -1`
+    return Date.parse(str)
+  end
+  
+  def gitmtime
+    # find file last modification time
+    filepath=@item[:content_filename]
+    str=`git log -1 --format=%cd --date=short -- #{filepath}`
+    return Date.parse(str)
+  end
+  
+
 end
diff --git a/lib/helpers/preprocess.rb b/lib/helpers/preprocess.rb
index 6c787de..dd3f3bb 100644
--- a/lib/helpers/preprocess.rb
+++ b/lib/helpers/preprocess.rb
@@ -52,12 +52,10 @@ module PreprocessHelper
 
   def update_blog_attributes
     @items.find_all('/blog/**/*.md').each do |i|
-      raise "#{i.identifier} doesn't have 'created_at'" unless i[:created_at]
       i.update_attributes(
         # Tag all posts with article (for Blogging helper)
         kind: 'article',
-        academic_year: i.identifier.to_s[/\d-\d/],
-        created_at: Date.parse(i[:created_at])
+        academic_year: i.identifier.to_s[/\d\d-\d\d/],
       )
     end
   end