my file is
column1 column2
1-Sep-11 31-Aug-12
1-May-12 30-Apr-14
1-Mar-09 28-Feb-14
1-Apr-13 31-Mar-14
1-Apr-10 31-Mar-13
i want how many years difference between column1 and column2
out put like
column1 column2
1-Sep-11 31-Aug-12 1
1-May-12 30-Apr-14 2
1-Mar-09 28-Feb-14 5
1-Apr-13 31-Mar-14 1
1-Apr-10 31-Mar-13 3
please let me know