If you go on to the Southwest web site and you'll see Flexible Dates (it's under Arrive and to the left of Promotion Code). If you click on that you'll be able to see the lowest pricing for every day in a month. So for PHX to BWI, 8/23 has flights for $179 and 8/27 from BWI to PHX $179. I stalk this calendar when I am looking for flights. It's easier than keep adjusting the dates. And remember to keep checking the pricing even after you purchase your flight. If the price/points decreases you can adjust and get the difference. I ended up with an $80 credit for my upcoming flight to Punta Cana since the price dropped twice.