diff --git a/engine/mysql.php b/engine/mysql.php
index 2c97e38..66c1400 100644
--- a/engine/mysql.php
+++ b/engine/mysql.php
@@ -2,6 +2,9 @@
 
 class mysql {
 
+    const DATE_FORMAT = 'Y-m-d';
+    const DATETIME_FORMAT = 'Y-m-d H:i:s';
+
     protected ?mysqli $link = null;
 
     function __construct(
diff --git a/lib/posts.php b/lib/posts.php
index 5c8aecf..d7a8b44 100644
--- a/lib/posts.php
+++ b/lib/posts.php
@@ -15,12 +15,18 @@ class Post extends model {
 
     public int $id;
     public string $date;
+    public ?string $updateTime;
     public bool $visible;
     public string $shortName;
     public string $sourceUrl;
 
     protected array $texts = [];
 
+    public function edit(array $fields) {
+        $fields['update_time'] = date(mysql::DATETIME_FORMAT, time());
+        parent::edit($fields);
+    }
+
     public function addText(PostLanguage $lang, string $title, string $md, bool $toc): ?PostText {
         $html = markup::markdownToHtml($md, lang: $lang);
         $text = markup::htmlToText($html);