Come impostare il timestamp predefinito su now() + n giorni?

es:

t=# create table t5(t timestamp default now() + '1 day'::interval);
CREATE TABLE
t=# insert into t5 default values;
INSERT 0 1
t=# select now(),t from t5;
              now              |             t
-------------------------------+----------------------------
 2018-01-26 08:05:06.641249+00 | 2018-01-27 08:04:57.035831
(1 row)