abap里边如何计算 两个日期之间的天数

*******DATA: date1 TYPE sy-datum,
*******      date2 TYPE sy-datum,
*******      date3 TYPE p.
*******
*******date1 = '20130125'.
*******date2 = '20130126'.
******* CALL FUNCTION 'SD_DATETIME_DIFFERENCE'
*******      EXPORTING
*******        date1            = date1
*******        time1            = '000001'
*******        date2            = date2
*******        time2            = '000001'
*******      IMPORTING
*******        datediff         = date3
********       TIMEDIFF         =
********       EARLIEST         =
*******      EXCEPTIONS
*******        invalid_datetime = 1
*******        OTHERS           = 2.
*******
******* WRITE: / date3.