diff --git a/tailbone/forms/core.py b/tailbone/forms/core.py
index 17921c72..850768cf 100644
--- a/tailbone/forms/core.py
+++ b/tailbone/forms/core.py
@@ -27,7 +27,6 @@ Forms Core
 from __future__ import unicode_literals, absolute_import
 
 import json
-import datetime
 import logging
 
 import six
@@ -36,7 +35,7 @@ from sqlalchemy import orm
 from sqlalchemy.ext.associationproxy import AssociationProxy, ASSOCIATION_PROXY
 
 from rattail.time import localtime
-from rattail.util import prettify, pretty_boolean, pretty_hours, pretty_quantity
+from rattail.util import prettify, pretty_boolean, pretty_quantity
 from rattail.core import UNSPECIFIED
 
 import colander
@@ -902,10 +901,11 @@ class Form(object):
         return raw_datetime(self.request.rattail_config, value)
 
     def render_duration(self, record, field_name):
-        value = self.obtain_value(record, field_name)
-        if value is None:
+        seconds = self.obtain_value(record, field_name)
+        if seconds is None:
             return ""
-        return pretty_hours(datetime.timedelta(seconds=value))
+        app = self.request.rattail_config.get_app()
+        return app.render_duration(seconds=seconds)
 
     def render_boolean(self, record, field_name):
         value = self.obtain_value(record, field_name)
diff --git a/tailbone/grids/core.py b/tailbone/grids/core.py
index d825e4b4..cb71e144 100644
--- a/tailbone/grids/core.py
+++ b/tailbone/grids/core.py
@@ -26,7 +26,6 @@ Core Grid Classes
 
 from __future__ import unicode_literals, absolute_import
 
-import datetime
 import warnings
 import logging
 
@@ -358,10 +357,11 @@ class Grid(object):
         return pretty_quantity(value)
 
     def render_duration(self, obj, column_name):
-        value = self.obtain_value(obj, column_name)
-        if value is None:
+        seconds = self.obtain_value(obj, column_name)
+        if seconds is None:
             return ""
-        return pretty_hours(datetime.timedelta(seconds=value))
+        app = self.request.rattail_config.get_app()
+        return app.render_duration(seconds=seconds)
 
     def render_duration_hours(self, obj, field):
         value = self.obtain_value(obj, field)