Here's a quick bug to try at home:
Book "Price and Schedule" for DFW to LGA 10/11 returning 10/13. Calendar is shown.
1. What is the price on the tab for 10/12? What about the 10/13 tab?
2. Now click the 10/12 tab, what is the price now? Do the same for 10/13.
For me, the 10/13 price on the TAB changed from $960 to $267!! That's quite a difference. I don't care what the fare rules are, that's a system bug.