diff --git a/boostjp/templates/content.html b/boostjp/templates/content.html
index 9654962..c3c41ef 100644
--- a/boostjp/templates/content.html
+++ b/boostjp/templates/content.html
@@ -92,8 +92,8 @@
   {% if latest_commit_info %}
     <p class="text-right"><small>
       最終更新日時:
-      <span itemprop="datePublished" content="{{ latest_commit_info['last_updated'].strftime('%Y-%m-%dT%H:%M:%S') }}">
-        {{ latest_commit_info['last_updated'].strftime('%Y年%m月%d日 %H時%M分%S秒') }}
+      <span itemprop="datePublished" content="{{ latest_commit_info['last_updated'].strftime('%Y-%m-%dT%H:%M:%S%z') }}">
+        {{ latest_commit_info['last_updated'].strftime('%Y年%m月%d日 %H時%M分%S秒') }} (JST)
       </span>
       <br/>
       <span itemprop="author" itemscope itemtype="http://schema.org/Person">
diff --git a/cpprefjp/templates/content.html b/cpprefjp/templates/content.html
index 952f458..7c6949c 100644
--- a/cpprefjp/templates/content.html
+++ b/cpprefjp/templates/content.html
@@ -101,9 +101,9 @@
 {% block latest_commit_info %}
   {% if latest_commit_info %}
     <p class="text-right"><small>
-      最終更新日時(UTC):
-      <span itemprop="datePublished" content="{{ latest_commit_info['last_updated'].strftime('%Y-%m-%dT%H:%M:%S') }}">
-        {{ latest_commit_info['last_updated'].strftime('%Y年%m月%d日 %H時%M分%S秒') }}
+      最終更新日時:
+      <span itemprop="datePublished" content="{{ latest_commit_info['last_updated'].strftime('%Y-%m-%dT%H:%M:%S%z') }}">
+        {{ latest_commit_info['last_updated'].strftime('%Y年%m月%d日 %H時%M分%S秒') }} (JST)
       </span>
       <br/>
       <span itemprop="author" itemscope itemtype="http://schema.org/Person">
diff --git a/run.py b/run.py
index ea18bee..11c81d7 100755
--- a/run.py
+++ b/run.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 
-from datetime import datetime
+from datetime import datetime, timedelta, timezone
 import glob
 import importlib
 import json
@@ -469,13 +469,17 @@ def flush(self):
             f.write(json.dumps(self._cache))
 
 
+_JST = timezone(timedelta(hours=9), 'JST')
+
+
 def get_latest_commit_info(path):
     commit_log = subprocess.check_output(['git', 'log', '-1', '--date=iso', '--pretty=format:%at %an', path + '.md'], cwd=settings.INPUT_DIR, text=True, errors='ignore')
     if not commit_log:
         return None
     timestamp, author = commit_log.split(' ', 1)
     return {
-        'last_updated': datetime.fromtimestamp(int(timestamp)),
+        # git の %at は Unix 時刻 (UTC の瞬間) なので JST に変換して返す。
+        'last_updated': datetime.fromtimestamp(int(timestamp), _JST),
         'last_author': author,
     }