Date time function f_delivery_time

create or replace function f_delivery_time(p_delivery_time varchar2, p_booking_time varchar2) return Char is
v number(10,4);
begin
v:=24*(to_date(p_delivery_time , 'DD-MON-RR HH24:MI:SS') - to_date(p_booking_time, 'DD-MON-RR HH24:MI:SS'));
return(v);
end;
/


select f_delivery_time('20-SEP-18 15:10:10','20-SEP-18 14:10:10') from dual;
1

EXEC DBMS_OUTPUT.PUT_LINE(f_delivery_time('20-SEP-18 15:10:10','20-SEP-18 14:10:10'));
1

/*
select end_date,start_date,
   trunc(months_between(end_date,start_date)/12) as yrs ,
   trunc(mod( months_between(end_date,start_date) ,12)) as mnts,
   trunc(end_date - add_months( start_date, months_between(end_date,start_date))) as dys,
  trunc(24*mod(end_date - start_date,1)) as hrs,
  trunc( mod(mod(end_date - start_date,1)*24,1)*60 ) as mins ,
  mod(mod(mod(end_date - start_date,1)*24,1)*60,1)*60 as secs
from ( select to_date('15/11/2015 11:19:58','dd/mm/yyyy hh24:mi:ss') end_date ,
to_date('14/10/2014 10:18:57','dd/mm/yyyy hh24:mi:ss') start_date
from dual );

*/