The information is out of synch with the market because the home owners themselves (or their real estate agents) are claiming the homes on Zillow and updating the status to "For Sale" within Zillow. This is not tied into the MLS or other real estate listing databases that would systematically track and update once a house was sold. The person who claimed the house in Zillow would have to update the status in Zillow. For homes in an on-going active (e.g., For Sale) status, Zillow periodically requests (every 6 months or so) that the person who claimed the home should update the status. If no action is taken, Zillow will revert the listing back to the default inactive status (e.g., Not For Sale).