diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index a07cae3cc87..c19db2646d0 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -1591,42 +1591,6 @@ function template_preprocess_datetime(&$variables) {
   $variables['attributes'] = new Attribute($variables['attributes']);
 }
 
-/**
- * Returns HTML for a date / time.
- *
- * @param $variables
- *   An associative array containing:
- *   - timestamp: (optional) A UNIX timestamp for the datetime attribute. If
- *     the datetime cannot be represented as a UNIX timestamp, use a valid
- *     datetime attribute value in $variables['attributes']['datetime'].
- *   - text: (optional) The content to display within the <time> element. Set
- *     'html' to TRUE if this value is already sanitized for output in HTML.
- *     Defaults to a human-readable representation of the timestamp value or
- *     the datetime attribute value using format_date().
- *     When invoked as #theme or #theme_wrappers of a render element, the
- *     rendered #children are autoamtically taken over as 'text', unless #text
- *     is explicitly set.
- *   - attributes: (optional) An associative array of HTML attributes to apply
- *     to the <time> element. A datetime attribute in 'attributes' overrides
- *     the 'timestamp'. To create a valid datetime attribute value from a UNIX
- *     timestamp, use format_date() with one of the predefined 'html_*'
- *     formats.
- *   - html: (optional) Whether 'text' is HTML markup (TRUE) or plain-text
- *     (FALSE). Defaults to FALSE. For example, to use a SPAN tag within the
- *     TIME element, this must be set to TRUE, or the SPAN tag will be escaped.
- *     It is the responsibility of the caller to properly sanitize the value
- *     contained in 'text' (or within the SPAN tag in aforementioned example).
- *
- * @see template_preprocess_datetime()
- * @see http://www.w3.org/TR/html5-author/the-time-element.html#attr-time-datetime
- */
-function theme_datetime($variables) {
-  $output = '<time' . new Attribute($variables['attributes']) . '>';
-  $output .= !empty($variables['html']) ? $variables['text'] : check_plain($variables['text']);
-  $output .= '</time>';
-  return $output;
-}
-
 /**
  * Returns HTML for status and/or error messages, grouped by type.
  *
diff --git a/core/modules/system/templates/datetime.html.twig b/core/modules/system/templates/datetime.html.twig
index 5ea386e35c9..25ef788989a 100644
--- a/core/modules/system/templates/datetime.html.twig
+++ b/core/modules/system/templates/datetime.html.twig
@@ -1,6 +1,7 @@
 {#
 /**
- * Returns HTML for a date / time.
+ * @file
+ * Default theme implementation for a date / time element.
  *
  * Available variables
  * - timestamp: (optional) A UNIX timestamp for the datetime attribute. If the
@@ -25,4 +26,4 @@
  */
 #}
 {# @todo Revisit once http://drupal.org/node/1825952 is resolved. #}
-<time class="{{ attributes.class }}" {{ attributes }}>{{ html ? text|raw : text|escape }}</time>
+<time{{ attributes }}>{{ html ? text|raw : text|escape }}</time>