How to calculate time difference between two dates?

--ORACLE

CREATE OR REPLACE FUNCTION DATETIMEDIFFCALC(FRMDATE DATE, TODATE DATE)

  RETURN VARCHAR2 AS

  V_OUT VARCHAR2(100);

  V_DAY  INTEGER;

  V_HR   INTEGER;

  V_MN   INTEGER;

BEGIN

  SELECT EXTRACT(DAY FROM DIFF),

         EXTRACT(HOUR FROM DIFF),

         EXTRACT(MINUTE FROM DIFF)

    INTO V_DAY, V_HR, V_MN

    FROM (SELECT (CAST(FRMDATE AS TIMESTAMP) - CAST(TODATE AS TIMESTAMP)) DIFF

            FROM DUAL);

  V_OUT := 'DAY : ' || V_DAY || ' HOUR : ' || V_HR || ' MIN : ' || V_MN;

  RETURN V_OUT;

END DATETIMEDIFFCALC;

--SQL

DECLARE @FROM_DATE DATETIME = '2017-03-01 12:12:12:122'

DECLARE @TO_DATE DATETIME = GETDATE()

SELECT CONCAT('DAY :',DATEDIFF(DAY,@FROM_DATE,@TO_DATE), ' HOUR :',DATEDIFF(HH,@FROM_DATE,@TO_DATE), ' MIN :',DATEDIFF(MM,@FROM_DATE,@TO_DATE))