How To Add Day, Hour, Minute, Second to a Date Value in Oracle

Add a day.
select to_date('02-22-2008 10:30:30','mm-dd-yyyy hh24:mi:ss') today,
to_date('02-22-2008 10:30:30','mm-dd-yyyy hh24:mi:ss')+1 next_day
from dual;
TODAY NEXT_DAY
------------------------- -------------------------
02-22-08 10:30:30 02-23-08 10:30:30

Add an hour.
select to_date('02-22-08 10:30:30','mm-dd-yy hh24:mi:ss') today,
to_date('02-22-08 10:30:30','mm-dd-yy hh24:mi:ss')+ 1/24 next_hour
from dual;
TODAY NEXT_HOUR
------------------------ ------------------------
02-22-08 10:30:30 02-22-08 11:30:30

Add a minute.
select to_date('02-22-08 10:30:30','mm-dd-yy hh24:mi:ss') today,
to_date('02-22-08 10:30:30','mm-dd-yy hh24:mi:ss')+ 1/(24*60) next_min
from dual;
TODAY NEXT_MIN
------------------------ ------------------------
02-22-08 10:30:30 02-22-08 10:31:30

Add a second.
select to_date('02-22-08 10:30:30','mm-dd-yy hh24:mi:ss') today,
to_date('02-22-08 10:30:30','mm-dd-yy hh24:mi:ss')+ 1/(24*60*60) next_sec
from dual;
TODAY NEXT_SEC
------------------------ ------------------------
02-22-08 10:30:30 02-22-08 10:30:31