diff --git a/Documentation/NuttxPortingGuide.html b/Documentation/NuttxPortingGuide.html
index e17a9c62e47..7d190a14620 100644
--- a/Documentation/NuttxPortingGuide.html
+++ b/Documentation/NuttxPortingGuide.html
@@ -4173,6 +4173,11 @@ build
       If you are willing to live with some non-standard, short long file names, then define this value.
       A good choice would be the same value as selected for CONFIG_NAME_MAX which will limit the visibility of longer file names anyway.
   </li>
+  <li>
+    <code>CONFIG_FS_FATTIME</code>: Support FAT date and time.
+    NOTE:  There is not much sense in supporting FAT date and time unless you have a hardware RTC
+    or other way to get the time and date.
+  </li>
   <li>
     <code>CONFIG_FS_NXFFS</code>: Enable NuttX FLASH file system (NXFF) support.
   </li>