Avec le name ça marche mieux

users/templates/users/datetimepicker.html

@@ -4,7 +4,7 @@
 <script src="/javascript/jquery-timepicker/jquery-ui-timepicker-addon.js"></script> 
 <link href="/javascript/jquery-ui/css/smoothness/jquery-ui.min.css" rel="stylesheet"/> 
 <link href="/javascript/jquery-timepicker/jquery-ui-timepicker-addon.css" rel="stylesheet"/> 
-<input {{attrs}} name="datetimepicker" type="text" class="form-control" placeholder="Date"/> 
+<input {{attrs}} name="{{name}}" type="text" class="form-control" placeholder="Date"/> 
 <script> 
 $(document).ready(function(){ 
 	$("#{{id}}").datetimepicker({

users/widgets.py

@@ -29,6 +29,7 @@ class DateTimePicker(Input):
         super().render(name, value, attrs) 
         flat_attrs = flatatt(attrs)
         context = Context({
+            'name': name,
             'attrs': flat_attrs, 
             'id': attrs['id'], 
             'closeText': _("Close"),