Question on Request date in Forecast (P3460)

Hi

When we run R3465 to populate F3460 with sales history details, all the demands for that particular period are rolled up and entered in F3460 with requested date as "last day of the period". Although the sales history shows for the entire period, R3465 populates the entire qty against last date of that period (weekly bucket).  We would like to populate the requested date as " first day of the period" (weekly bucket)" in P3460 whenever we run R3465. Not sure about business reason for this standard design.

Is this requested date populated based on 52 week period setup or shop floor calendar setup ?