diff --git a/lib/jekyll/filters.rb b/lib/jekyll/filters.rb
index 3020bfbc..ea0fc905 100644
--- a/lib/jekyll/filters.rb
+++ b/lib/jekyll/filters.rb
@@ -352,7 +352,7 @@ module Jekyll
         raise Errors::InvalidDateError,
           "Invalid Date: '#{input.inspect}' is not a valid datetime."
       end
-      date.to_time.localtime
+      date.to_time.dup.localtime
     end
 
     private