select current_date - '2017-01-01',
       extract(day from now()::timestamp - '2017-01-01 00:00:00'),
       extract(day from now()            - '2017-01-01 00:00:00Z');

select make_interval(days => ((extract(epoch from '2016-04-10'::date) - extract(epoch from '2016-02-10'::date))/(60*60*24))::integer)::text;

select format('%1$s days', ((extract(epoch from '2016-04-10'::date) - extract(epoch from '2016-02-10'::date))/(60*60*24))::integer);