diff --git a/changelog.md b/changelog.md
index 2162d369..f3fbbbf7 100644
--- a/changelog.md
+++ b/changelog.md
@@ -53,6 +53,7 @@ This is a major update that breaks backwards compatibility.
 * Throw an exception when trying to send a message with an empty body caused by an internal error.
 * Replaced all use of MD5 and SHA1 hash functions with SHA256.
 * Now checks for invalid host strings when sending via SMTP.
+* Include timestamps in HTML-format debug output
 
 ## Version 5.2.23 (March 15th 2017)
 * Improve trapping of TLS errors during connection so that they don't cause warnings, and are reported better in debug output
diff --git a/src/SMTP.php b/src/SMTP.php
index eb9b1165..21a37099 100644
--- a/src/SMTP.php
+++ b/src/SMTP.php
@@ -231,7 +231,7 @@ class SMTP
                 break;
             case 'html':
                 //Cleans up output a bit for a better looking, HTML-safe output
-                echo htmlentities(
+                echo gmdate('Y-m-d H:i:s') . ' ' . htmlentities(
                     preg_replace('/[\r\n]+/', '', $str),
                     ENT_QUOTES,
                     'UTF-8'