Date difference to hour minute (Duty time calculation)

 CREATE OR REPLACE FUNCTION DF_DATE_DIFF_TO_HOUR_MIN (pSDATE   DATE,

                                                     pEDATE   DATE)

    RETURN VARCHAR2

AS

    vHOUR_MIN   VARCHAR2 (200);

BEGIN

    SELECT    NVL(TO_CHAR (TRUNC (Seconds_ / (60 * 60)), 'FM9900'),0)

           || ':'

           || NVL(TRUNC (MOD (Seconds_, 60 * 60) / 60),0)

           || ':'

           || NVL(TRUNC(MOD (Seconds_, 60),2),0) INTO   vHOUR_MIN

      FROM (SELECT (pEDATE - (pSDATE - 0 / 24)) * 24 * 60 * 60    AS Seconds_

              FROM DUAL);

    RETURN vHOUR_MIN;

END;

SELECT DF_DATE_DIFF_TO_HOUR_MIN(:pSDATE, :pEDATE) FROM DUAL;