[glib] docs: Document poppler_annot_markup_get_date()
diff --git a/glib/poppler-annot.cc b/glib/poppler-annot.cc
index 5d8f2ea..62a0879 100644
--- a/glib/poppler-annot.cc
+++ b/glib/poppler-annot.cc
@@ -845,6 +845,15 @@
   annot->setOpacity(opacity);
 }
 
+/**
+ * poppler_annot_markup_get_date:
+ * @poppler_annot: a #PopplerAnnotMarkup
+ *
+ * Returns the date and time when the annotation was created
+ *
+ * Return value: (transfer full): a #GDate representing the date and time
+ *               when the annotation was created, or %NULL
+ */
 GDate *
 poppler_annot_markup_get_date (PopplerAnnotMarkup *poppler_annot)
 {