oracle difference between two dates in hours code example

Example 1: oracle difference between two dates in years

select floor(months_between(date '2012-10-10', date '2011-10-10') /12) from dual;

select floor(months_between(date '2012-10-9' , date '2011-10-10') /12) from dual;

Example 2: oracle difference between two dates in days

v_numvar := dt1-dt2;