Many thanks Amigo!!
I make an alternate solution, as my data was comming from postgresql I create an sql statement into the datasource to get the values:
select LPAD(punto_venta::text,4,'0') AS PtoVta, LPAD(numeracion::text,8,'0') AS Numeracion,
to_char(to_date(substring(fechaemision from 1 for
,'YYYYMMDD'),'DD/MM/YYYY') AS fechaemision,
to_char(to_date(substring(fechainiactividades from 1 for
,'YYYYMMDD'),'DD/MM/YYYY') AS fechainiactividades
from comprobantes_encabezado
where id = $V{IDComprobante}