Check dates Postgres

I need help with a query what I want is that I need to calculate the months of a worker of a company and add them with all the other contracts he had.

EJ: If you started working on a date like 06/15/2016 until 06/15/2018 (24 months), but you suddenly decided to retire from That company and then later decided to return and now has a contract from 04/16/2018 to 04/16/2019 (12 months) I need to add all those months for each worker (36 months). Your answer would be very helpful.

This is what I have but I can not specify what I need:

<?php 

            $query=$obj->post_ejecutar("SELECT * FROM datoscontractuales WHERE estado NOT IN (4, 5, 6)");

            while ($row=pg_fetch_array($query)) {

                $años=(strtotime($row["fecinicio"])-strtotime($row["fecfin"]))/(30*60*60*24);
                //La función abs lo que hace es sacar el valor absoluto de el valor recibido
                $años=abs($años); 
                //Redondea un número decimal
                $años=floor($años);

                echo $años;

            }


?>