diff --git a/doc/source/_exts/page_context.py b/doc/source/_exts/page_context.py
new file mode 100644
index 000000000..20830fc4f
--- /dev/null
+++ b/doc/source/_exts/page_context.py
@@ -0,0 +1,96 @@
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import datetime
+import os.path
+import subprocess
+
+from sphinx.util import logging
+
+LOG = logging.getLogger('page_context')
+
+_default_last_updated = datetime.datetime.now()
+
+
+def _get_last_updated_file(src_file):
+    if not os.path.exists(src_file):
+        return None
+    try:
+        last_updated_t = subprocess.check_output(
+            [
+                'git', 'log', '-n1', '--format=%ad',
+                '--date=format:%Y-%m-%d %H:%M:%S',
+                '--', src_file,
+            ]
+        ).decode('utf-8').strip()
+    except subprocess.CalledProcessError as err:
+        LOG.info('[governance] Could not get modification time of %s: %s',
+                 src_file, err)
+    else:
+        if last_updated_t:
+            try:
+                return datetime.datetime.strptime(last_updated_t,
+                                                  '%Y-%m-%d %H:%M:%S')
+            except ValueError as err:
+                LOG.info('[governance] Could not parse modification time of '
+                         '%s: %r',
+                         src_file, last_updated_t)
+    return None
+
+
+def _get_last_updated(app, pagename):
+    last_updated = None
+    full_src_file = app.builder.env.doc2path(pagename)
+
+    candidates = []
+
+    # Strip the prefix from the filename so the git command recognizes
+    # the file as part of the current repository.
+    src_file = full_src_file[len(app.builder.env.srcdir):].lstrip('/')
+    candidates.append(src_file)
+
+    if not os.path.exists(src_file):
+        # Some of the files are in doc/source and some are not. Some
+        # of the ones that are not are symlinked. If we can't find the
+        # file after stripping the full prefix, try looking for it in
+        # doc/source explicitly.
+        candidates.append(os.path.join('doc/source', src_file))
+
+    if pagename.startswith('reference/projects/'):
+        # If the file is in the reference/projects directory, it may
+        # be an auto-generated project page. In that case, use the
+        # YAML file as the source of the last_updated timestamp.
+        candidates.append('reference/projects.yaml')
+
+    for filename in candidates:
+        last_updated = _get_last_updated_file(filename)
+        if last_updated:
+            LOG.info('[governance] Last updated for %s is %s',
+                     pagename, last_updated)
+            return last_updated
+    LOG.info('[governance] could not determine last_updated for %r',
+             pagename)
+    return _default_last_updated
+
+
+def html_page_context(app, pagename, templatename, context, doctree):
+    # Use the last modified date from git instead of applying a single
+    # value to the entire site.
+    context['last_updated'] = _get_last_updated(app, pagename)
+
+
+def setup(app):
+    LOG.info('[governance] connecting html-page-context event handler')
+    app.connect('html-page-context', html_page_context)
+    return {
+        'parallel_read_safe': True,
+    }
diff --git a/doc/source/conf.py b/doc/source/conf.py
index 6e3af532b..63b01eb28 100644
--- a/doc/source/conf.py
+++ b/doc/source/conf.py
@@ -13,6 +13,7 @@
 
 # flake8: noqa
 
+import datetime
 import subprocess
 import sys
 import os
@@ -39,6 +40,7 @@ extensions = [
     'teams',
     'tags',
     'badges',
+    'page_context',
 ]
 
 todo_include_todos = True
@@ -141,10 +143,7 @@ html_extra_path = ['_extra']
 
 # If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
 # using the given strftime format.
-git_cmd = ["git", "log", "--pretty=format:'%ad, commit %h'", "--date=local",
-           "-n1"]
-html_last_updated_fmt = str(subprocess.Popen(
-    git_cmd, stdout=subprocess.PIPE).communicate()[0])
+html_last_updated_fmt = '%Y-%m-%d'
 
 # If true, SmartyPants will be used to convert quotes and dashes to
 # typographically correct entities.