diff --git a/mod/data/field/date/field.class.php b/mod/data/field/date/field.class.php
index 5a3f3b98e7a..97848814f44 100644
--- a/mod/data/field/date/field.class.php
+++ b/mod/data/field/date/field.class.php
@@ -198,7 +198,7 @@ class data_field_date extends data_field_base {
 
     function get_sort_sql($fieldname) {
         global $DB;
-        return $DB->sql_cast_char2int($fieldname, true);
+        return $DB->sql_cast_char2real($fieldname, true);
     }
 
     /**