Travelocity starts out showing you a calendar of dates that the rules for your fare allow you to travel (blue). It doesn't show you what days the fare is not yet sold out. Not until you click on a date does it actually check to see if the fare class is available. Often times the fare is actually sold out for much if not all of the dates that are valid for the fare.
I think the reason why Travelocity doesn't just show you what days the fare is still actually available is because seat inventories are constantly changing, and it would take too much computer time on Travelocity's servers to check seat inventories for every flight of every day every single times someone pulls up a calendar. You can already see how slow it is for Travelocity to check one click (a 7 day period). Imagine how long it would take to do many months of flights.
The servers would slow to a crawl and travelocity would become unusable if they checked all the flights on all the days.
Having said this, I think that this can be fixed. Currently, it appears that Travelocity is querying the CRS (the airline's computers) every time somebody clicks on a date on the calendar. If travelocity could cache the fare inventory data on its own servers so that it can be re-used for subsequent queries, then the delay of sending the request to the CRS and waiting for it to respond could be eliminated. The cached data could expire in a matter of minutes so that the data does not become too out of date, because cached data can erroneously show a flight to be available when it is actually just sold out.
Just my thoughts...