diff --git a/lib/jekyll/filters.rb b/lib/jekyll/filters.rb
index 5972aad6..e76fa755 100644
--- a/lib/jekyll/filters.rb
+++ b/lib/jekyll/filters.rb
@@ -1,5 +1,6 @@
 require 'uri'
 require 'json'
+require 'date'
 
 module Jekyll
   module Filters