fixed a doc anchor

doc/filters/date.rst

@@ -53,13 +53,14 @@ The default timezone can also be set globally by calling ``setTimezone()``:
     $twig = new Twig_Environment($loader);
     $twig->getExtension('core')->setTimezone('Europe/Paris');
 
-.. _`strtotime`:    http://www.php.net/strtotime
-.. _`DateTime`:     http://www.php.net/DateTime
-.. _`DateInterval`: http://www.php.net/DateInterval
-
-If the value passed to the ``date`` filter is null, it will return the current date by default.
-If an empty string is desired instead of the current date, use a ternary operator:
+If the value passed to the ``date`` filter is ``null``, it will return the
+current date by default. If an empty string is desired instead of the current
+date, use a ternary operator:
 
 .. code-block:: jinja
 
     {{ post.published_at is empty ? "" : post.published_at|date("m/d/Y") }}
+
+.. _`strtotime`:    http://www.php.net/strtotime
+.. _`DateTime`:     http://www.php.net/DateTime
+.. _`DateInterval`: http://www.php.net/DateInterval

doc/filters/date_modify.rst

@@ -10,9 +10,9 @@ The ``date_modify`` filter modifies a date with a given modifier string:
 
     {{ post.published_at|date_modify("+1 day")|date("m/d/Y") }}
 
-The ``date_modify`` filter accepts strings (it must be in a format supported by the
-`strtotime`_ function) or `DateTime`_ instances. You can easily combine it with the `date`_
-filter for formatting.
+The ``date_modify`` filter accepts strings (it must be in a format supported
+by the `strtotime`_ function) or `DateTime`_ instances. You can easily combine
+it with the :doc:`date </filters/date>` filter for formatting.
 
 .. _`strtotime`:    http://www.php.net/strtotime
 .. _`DateTime`:     http://www.php.net/DateTime