Availability is always calculated based on the expected ready dates of your inventory in relation to the commitments for scheduled ship dates. Whether you are taking orders for next day or a year in advance, you will always know the quantity you have available to meet your customers' requested ship date.
Plant Partnertm's availability formula is designed specifically to match your unique inventory operation. In Plant Partnertm you can specify a sell window for each type of product you produce. The sell window is essentially how long can you keep the product around before it absolutely has to ship or be wasted. This enables you to meet high demand for a particular ship week.
For example, XYZ Nursery wants a shipment of Impatiens 1204 on the first week of May. The crop of Impatiens coming ready on the first week of May is already sold out. You don't want the salesperson to tell the customer you can't ship that week. If there are unsold Impatiens coming ready the last week of April you could certainly keep them around for a week, maybe even two if necessary. Plant Partnertm has the ability to sum up unsold items for several weeks and display the total as available.