diff --git a/django/contrib/sitemaps/tests/test_http.py b/django/contrib/sitemaps/tests/test_http.py
index c3c5767d49..cf0cc38732 100644
--- a/django/contrib/sitemaps/tests/test_http.py
+++ b/django/contrib/sitemaps/tests/test_http.py
@@ -82,6 +82,21 @@ class HTTPSitemapTests(SitemapTestsBase):
         response = self.client.get('/lastmod/sitemap.xml')
         self.assertEqual(response['Last-Modified'], 'Wed, 13 Mar 2013 10:00:00 GMT')
 
+    def test_sitemap_last_modified_date(self):
+        """
+        The Last-Modified header should be support dates (without time).
+        """
+        response = self.client.get('/lastmod/date-sitemap.xml')
+        self.assertEqual(response['Last-Modified'], 'Wed, 13 Mar 2013 00:00:00 GMT')
+
+    def test_sitemap_last_modified_tz(self):
+        """
+        The Last-Modified header should be converted from timezone aware dates
+        to GMT.
+        """
+        response = self.client.get('/lastmod/tz-sitemap.xml')
+        self.assertEqual(response['Last-Modified'], 'Wed, 13 Mar 2013 15:00:00 GMT')
+
     def test_sitemap_last_modified_missing(self):
         "Tests that Last-Modified header is missing when sitemap has no lastmod"
         response = self.client.get('/generic/sitemap.xml')
diff --git a/django/contrib/sitemaps/tests/urls/http.py b/django/contrib/sitemaps/tests/urls/http.py
index c232958074..87bbb1e509 100644
--- a/django/contrib/sitemaps/tests/urls/http.py
+++ b/django/contrib/sitemaps/tests/urls/http.py
@@ -1,8 +1,9 @@
-from datetime import datetime
+from datetime import date, datetime
 from django.conf.urls import url
 from django.conf.urls.i18n import i18n_patterns
 from django.contrib.sitemaps import Sitemap, GenericSitemap, FlatPageSitemap, views
 from django.http import HttpResponse
+from django.utils import timezone
 from django.views.decorators.cache import cache_page
 
 from django.contrib.sitemaps.tests.base import I18nTestModel, TestModel
@@ -53,6 +54,14 @@ class FixedLastmodMixedSitemap(Sitemap):
         return [o1, o2]
 
 
+class DateSiteMap(SimpleSitemap):
+    lastmod = date(2013, 3, 13)
+
+
+class TimezoneSiteMap(SimpleSitemap):
+    lastmod = datetime(2013, 3, 13, 10, 0, 0, tzinfo=timezone.get_fixed_timezone(-300))
+
+
 def testmodelview(request, id):
     return HttpResponse()
 
@@ -99,6 +108,10 @@ urlpatterns = [
     url(r'^empty/sitemap\.xml$', views.sitemap, {'sitemaps': empty_sitemaps}),
     url(r'^lastmod/sitemap\.xml$', views.sitemap, {'sitemaps': fixed_lastmod_sitemaps}),
     url(r'^lastmod-mixed/sitemap\.xml$', views.sitemap, {'sitemaps': fixed_lastmod__mixed_sitemaps}),
+    url(r'^lastmod/date-sitemap.xml$', views.sitemap,
+        {'sitemaps': {'date-sitemap': DateSiteMap}}),
+    url(r'^lastmod/tz-sitemap.xml$', views.sitemap,
+        {'sitemaps': {'tz-sitemap': TimezoneSiteMap}}),
     url(r'^generic/sitemap\.xml$', views.sitemap, {'sitemaps': generic_sitemaps}),
     url(r'^flatpages/sitemap\.xml$', views.sitemap, {'sitemaps': flatpage_sitemaps}),
     url(r'^cached/index\.xml$', cache_page(1)(views.index),
diff --git a/django/contrib/sitemaps/views.py b/django/contrib/sitemaps/views.py
index aa184e99bd..a743f6e614 100644
--- a/django/contrib/sitemaps/views.py
+++ b/django/contrib/sitemaps/views.py
@@ -1,4 +1,5 @@
 from calendar import timegm
+import datetime
 from functools import wraps
 
 from django.contrib.sites.shortcuts import get_current_site
@@ -74,6 +75,11 @@ def sitemap(request, sitemaps, section=None,
     if hasattr(site, 'latest_lastmod'):
         # if latest_lastmod is defined for site, set header so as
         # ConditionalGetMiddleware is able to send 304 NOT MODIFIED
+        lastmod = site.latest_lastmod
         response['Last-Modified'] = http_date(
-            timegm(site.latest_lastmod.utctimetuple()))
+            timegm(
+                lastmod.utctimetuple() if isinstance(lastmod, datetime.datetime)
+                else lastmod.timetuple()
+            )
+        )
     return response
diff --git a/docs/releases/1.7.1.txt b/docs/releases/1.7.1.txt
index 98e99e8125..8e45850437 100644
--- a/docs/releases/1.7.1.txt
+++ b/docs/releases/1.7.1.txt
@@ -40,3 +40,6 @@ Bugfixes
 
 * Empty ``index_together`` or ``unique_together`` model options no longer
   results in infinite migrations (:ticket:`23452`).
+
+* Fixed crash in ``contrib.sitemaps`` if ``lastmod`` returned a ``date`` rather
+  than a ``datetime`` (:ticket:`23403`).