gistfile1.txt

create table f (
  i interval
);

insert into f values ('4 days');
insert into f values ('6 years');
insert into f values ('30 minute');

select * from f;
----------
 4 days
 6 years
 00:30:00
(3 rows)

select now(), now() + i from f;
-------------------------------+-------------------------------
 2013-05-08 15:34:30.052171-07 | 2013-05-12 15:34:30.052171-07
 2013-05-08 15:34:30.052171-07 | 2019-05-08 15:34:30.052171-07
 2013-05-08 15:34:30.052171-07 | 2013-05-08 16:04:30.052171-07