Added the versionadded directive

Author: javiereguiluz

reference/forms/types/time.rst

@@ -161,6 +161,10 @@ reference_date
 
 **type**: ``DateTimeInterface`` **default**: ``null``
 
+.. versionadded:: 4.4
+
+    The ``reference_date`` option was introduced in Symfony 4.4.
+
 Configuring a reference date is required when the `model_timezone`_ and
 `view_timezone`_ are different. Timezone conversions will be calculated
 based on this date.