The reason is that you work on products, but you live in periods. Thus, the project schedule must address product needs but conform to the realities of your calendar. Figure 1 shows how product and period planning are related in a business. Engineering develops products for release to manufacturing, marketing, and the customer. Engineering also sends product plans to the finance department which produces price and forecast information for manufacturing and marketing.
Finance also generates cost and revenue projections for corporate.
Corporate management then decides what dividends to pay the investors and how much they can spend on marketing, manufacturing, and new product development. They then provide the needed period funding. This window will remain open to display figures in this file, although it might be hidden behind other browser windows. Period planning is important to you. You get paid in periods and management needs period cash flow to get the money to pay you.