softwareheritage=> select now() at time zone interval '00:00';
          timezone          
----------------------------
 2020-05-24 13:31:01.133371
(1 row)

softwareheritage=> select now() at time zone interval ('00:' || '00');
ERROR:  syntax error at or near "'00:'"
LINE 1: select now() at time zone interval ('00:' || '00');
                                            ^
softwareheritage=>