-- string to date
to_date("2013-02-01 13:04:00", 'YYYY-MM-DD HH24:MI:SS')


-- date to string
to_char(sysdate, 'YYYY-MM-DD HH24:MI:SS')


-- unixtime to date
to_date('01-01-1970', 'DD-MM-YYYY')+ (sysdate / ( 60*60*24) - (5/24))
to_date('01-01-1970', 'DD-MM-YYYY')+ (sysdate/1000 / ( 60*60*24) - (5/24)) -- java


-- date to unixtime
round((to_date(sysdate, 'YYYY-MM-DD HH24:MI:SS') - to_date('01-01-1970','DD-mm-YYYY')) * (86400))
round((to_date(sysdate, 'YYYY-MM-DD HH24:MI:SS') - to_date('01-01-1970','DD-mm-YYYY')) * (86400)*1000) -- java