I tried to follow the related documentation, here: http://jmsyst.com/libs/serializer/master/configuration here http://jmsyst.com/libs/serializer/master/handlers<
The solution is to create a service with the right tag.
datetimezone_handler: class: MyVendor\MyBundle\Serializer\Handler\DateTimeZoneHandler tags: - { name: jms_serializer.subscribing_handler }