diff --git a/README.md b/README.md
index e8f74e0..6672013 100644
--- a/README.md
+++ b/README.md
@@ -55,9 +55,9 @@ Function Reference
 
 The supported list of display functions is shown below:
 
-- `moment(timestamp=None, local=False).format(format_string)`
-- `moment(timestamp=None, local=False).fromNow(no_suffix = False)`
-- `moment(timestamp=None, local=False).fromTime(another_timesatmp, no_suffix = False)`
+- `moment(timestamp=None, local=False).format(format_string=None)`
+- `moment(timestamp=None, local=False).fromNow(no_suffix=False)`
+- `moment(timestamp=None, local=False).fromTime(another_timesatmp, no_suffix=False)`
 - `moment(timestamp=None, local=False).calendar()`
 - `moment(timestamp=None, local=False).valueOf()`
 - `moment(timestamp=None, local=False).unix()`
@@ -69,6 +69,11 @@ Auto-Refresh
 
 All the display functions take an optional `refresh` argument that when set to `True` will re-render timestamps every minute. This can be useful for relative time formats such as the one returned by the `fromNow()` or `fromTime()` functions. By default refreshing is disabled.
 
+Default Format
+--------------
+
+The `format()` function can be invoked without arguments, in which case a default format of ISO8601 defined by the moment.js library is used. If you want to set a different default, you can set the `MOMENT_DEFAULT_FORMAT` variable in the Flask configuration. Consult the [moment.js format documentation](http://momentjs.com/docs/#/displaying/format/) for a list of acepted tokens.
+
 Internationalization
 --------------------
 
diff --git a/flask_moment.py b/flask_moment.py
index 2045500..a2ae4bb 100644
--- a/flask_moment.py
+++ b/flask_moment.py
@@ -42,8 +42,12 @@ def include_moment(version=default_moment_version, local_js=None,
                          'crossorigin="anonymous"></script>\n' \
                          % (version, js_filename, sri)
 
+        default_format = ''
+        if 'MOMENT_DEFAULT_FORMAT' in current_app.config:
+            default_format = '\nmoment.defaultFormat = "%s";' % \
+                current_app.config['MOMENT_DEFAULT_FORMAT']
         return Markup('''%s<script>
-moment.locale("en");
+moment.locale("en");%s
 function flask_moment_render(elem) {
     $(elem).text(eval('moment("' + $(elem).data('timestamp') + '").' + $(elem).data('format') + ';'));
     $(elem).removeClass('flask-moment').show();
@@ -59,7 +63,7 @@ def include_moment(version=default_moment_version, local_js=None,
 $(document).ready(function() {
     flask_moment_render_all();
 });
-</script>''' % js)  # noqa: E501
+</script>''' % (js, default_format))  # noqa: E501
 
     @staticmethod
     def include_jquery(version=default_jquery_version, local_js=None,
@@ -119,8 +123,8 @@ def _render(self, format, refresh=False):
                        'style="display: none">%s</span>') %
                       (t, format, int(refresh) * 60000, t))
 
-    def format(self, fmt, refresh=False):
-        return self._render("format('%s')" % fmt, refresh)
+    def format(self, fmt=None, refresh=False):
+        return self._render("format('%s')" % (fmt or ''), refresh)
 
     def fromNow(self, no_suffix=False, refresh=False):
         return self._render("fromNow(%s)" % int(no_suffix), refresh)
diff --git a/tests/test_flask_moment.py b/tests/test_flask_moment.py
index d454a9e..c0ad46c 100644
--- a/tests/test_flask_moment.py
+++ b/tests/test_flask_moment.py
@@ -85,8 +85,15 @@ def test_include_moment_renders_properly(self, app, moment):
         ts = str(render_template_string("{{ moment.include_moment() }}"))
 
         assert "<script" in ts
-        assert default_moment_version + "/moment-with-locales.min.js" in str(
-            ts)
+        assert default_moment_version + "/moment-with-locales.min.js" in ts
+        assert 'moment.defaultFormat' not in ts
+
+    def test_include_moment_with_default(self, app, moment):
+        app.config['MOMENT_DEFAULT_FORMAT'] = 'foo'
+        ts = str(render_template_string("{{ moment.include_moment() }}"))
+        assert "<script" in ts
+        assert default_moment_version + "/moment-with-locales.min.js" in ts
+        assert 'moment.defaultFormat = "foo";' in ts
 
     def test_include_jquery_default(self):
         include_jquery = _moment.include_jquery()