Oracle two dates differance (Buddhist year)

SELECT to_date('29/09/2559', 'DD/MM/YYYY') -to_date('25/09/2559', 'DD/MM/YYYY') FROM dual;

Test result on Toad for Oracle

TO_DATE('29/09/2559','DD/MM/YYYY')-TO_DATE('25/09/2559','DD/MM/YYYY')

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                                                                    4

1 row selected.