diff --git a/js/outdated.js b/js/outdated.js
new file mode 100644
index 0000000..10b1262
--- /dev/null
+++ b/js/outdated.js
@@ -0,0 +1,35 @@
+/**
+ * MIT License
+ *
+ * Copyright (c) 2024 Zerocracy
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to who_namem the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+$(function() {
+  const dob = Date.parse($("time[itemprop='datePublished']").attr("datetime"));
+  const hours = parseInt((new Date() - dob) / (1000 * 60 * 60));
+  if (hours > 24) {
+    $("article").prepend(
+      "<p class='warning'><span>" +
+      "This page was generated " + hours + " hours ago. " +
+      "The information is most probably outdated.</span></p>"
+    );
+  }
+});
diff --git a/sass/main.scss b/sass/main.scss
index 759b167..1fb95e9 100644
--- a/sass/main.scss
+++ b/sass/main.scss
@@ -68,6 +68,17 @@ header {
     }
 }
 
+.warning {
+    text-align: center;
+
+    span {
+         background: darkred;
+         color: white;
+         padding: .5em 1em;
+         border-radius: .3em;
+    }
+}
+
 .ff {
     font-family: monospace;
 }
diff --git a/xsl/vitals.xsl b/xsl/vitals.xsl
index 25033c4..f07577f 100644
--- a/xsl/vitals.xsl
+++ b/xsl/vitals.xsl
@@ -199,7 +199,9 @@ SOFTWARE.
                 <xsl:value-of select="$version"/>
               </span>
               <xsl:text>) on </xsl:text>
-              <xsl:value-of select="current-dateTime()"/>
+              <time itemprop="datePublished" datetime="{current-dateTime()}">
+                <xsl:value-of select="current-dateTime()"/>
+              </time>
               <xsl:text>.</xsl:text>
               <br/>
               <a href="https://github.com/yegor256/factbase">