DAYS_BETWEEN_TWO_DATES-Can any one explain I_STGMETH field

Hi Experts,

I am using the Function Module DAYS_BETWEEN_TWO_DATES to calculate the difference between two dates

CALL FUNCTION 'DAYS_BETWEEN_TWO_DATES'
        EXPORTING
          i_datum_bis = 20080401
          i_datum_von = 20080327
        IMPORTING
          e_tage      = lv_diff.

The lv_day_diff is '4'

and

CALL FUNCTION 'DAYS_BETWEEN_TWO_DATES'
        EXPORTING
          i_datum_bis = 20080401
          i_datum_von = 20080327
          I_STGMETH   = 2
        IMPORTING
          e_tage      = lv_day_diff.

The lv_day_diff is 5

What is the importance of I_STGMETH..........

Thanks,

Chaitanya