diff --git a/docs/_docs/permalinks.md b/docs/_docs/permalinks.md
index 1a8afebac9b..31515b6b4ea 100644
--- a/docs/_docs/permalinks.md
+++ b/docs/_docs/permalinks.md
@@ -116,6 +116,14 @@ The following table lists the template variables available for permalinks. You c
         </p>
       </td>
     </tr>
+    <tr>
+      <td>
+        <p><code>y_day</code></p>
+      </td>_
+      <td>
+        <p>Day of the year from the post's filename, with leading zeros.</p>
+      </td>
+    </tr>
     <tr>
       <td>
         <p><code>short_year</code></p>