25 hour day

alter session set TIME_ZONE = 'Europe/Helsinki';

select to_timestamp_tz('28032010','ddmmyyyy') 
     + interval '3' hour 
     + interval '30' minute as a
from dual;

28.3.2010 4:30:00.000000000 +03:00 

select to_timestamp_tz('31102010','ddmmyyyy')
     + interval '3' hour 
     + interval '30' minute as b
from dual;

31.10.2010 3:30:00.000000000 +03:00 

select to_timestamp_tz('31102010','ddmmyyyy') 
     + interval '4' hour 
     + interval '30' minute as c
from dual;

31.10.2010 3:30:00.000000000 +02:00 

select to_timestamp_tz('31102010','ddmmyyyy') 
     + interval '24' hour 
     + interval '30' minute as d
from dual;

31.10.2010 23:30:00.000000000 +02:00