Schedule lines

Hi Gurus,

what are the factors that effect the scedule lines for a material?

whenever a sales order is created the schedule lines at the sales order line item level shows the schedules in future dates...i want to have the schedule lines in current dates...VOV8 settings shows the proposed delivery date in the sales order type is marked on and the Lead time is Zero .and the stock requirement list (MD04) shows the qty as available as on date .

can anyone let me know what else will effect the schedule lines

Thanks

Ivy