The calendar operates on a fare-based award system, which instead of using a fixed award chart, calculates the amount of points required for a flight based on the cash price of the ticket. It facilitates simultaneous comparison of flight costs on several days or months. It's simple to calculate the price difference if you decide to travel on a different day than you had originally planned because various days can be significantly less expensive depending on your main trip date. Visit: Southwest Low-Fare Calendar