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create table the_table
(
id int primary key,
"start" timestamp,
"end" timestamp
);
insert into the_table
values
(1, '2022-05-07 06:00', '2022-05-09 12:00'),
(2, '2022-05-08 04:00', '2022-05-12 03:30');
select t.id,
case
when t.start::date = x.dt::date then t.start
else date_trunc('day', x.dt)
end as "start",
case
when t.end::date = x.dt::date then t.end
else (x.dt::date + 1)::timestamp
end as "end"
from the_table t
cross join generate_series(t.start, t.end, interval '1 day') as x(dt)
order by t.id, "start"
