--- /dev/null
+<?php
+
+namespace Drupal\metatag_open_graph\Plugin\metatag\Tag;
+
+use \Drupal\metatag\Plugin\metatag\Tag\MetaPropertyBase;
+
+/**
+ * The Open Graph "Article modified time" meta tag.
+ *
+ * @MetatagTag(
+ * id = "article_modified_time",
+ * label = @Translation("Article modification date & time"),
+ * description = @Translation("The date this content was last modified, with an optional time value. Needs to be in <a href='http://en.wikipedia.org/wiki/ISO_8601'>ISO 8601</a> format."),
+ * name = "article:modified_time",
+ * group = "open_graph",
+ * weight = 33,
+ * type = "label",
+ * secure = FALSE,
+ * multiple = FALSE
+ * )
+ */
+class ArticleModifiedTime extends MetaPropertyBase {
+ // Nothing here yet. Just a placeholder class for a plugin.
+}