period of forecast and forecast allocation and consumption

All,

As I know, when we define a forecase(demand) for a material, we can define it in period monthly , weekly or dayly, both in APO and ECC.

But we only can define the allocation and consumption as backward or forward and No. of days.

It seems that we can define forecase monthly, but we can define the allocation and consumption monthly. Am I right?

Such as  forecase in Sep. is 1000pc, consumpstion backward 30 Days, but some of orders in Oct. can allocation and consumpte this forecase.

Is this SAP standard?

How can we do the forecase and allocation and consumption monthly?

means forecase in Sep. , only the orders in Sep. can allocated and consumpte this forecase.

Thanks.