http://www.zillow.com/advice-thread/I-can-not-find-info-about-what-the-30-day-change-is-all-about-could-you-please-answer-that-question/198296/ Zillow Advice | Zillow Real Estate http://www.zillow.com/advice-thread/I-can-not-find-info-about-what-the-30-day-change-is-all-about-could-you-please-answer-that-question/198296/ Here is a zillow blog link that has some information on it burried in there.&nbsp; Hope that helps a bit:<br/><a rel="nofollow" href="http://www.zillowblog.com/explaining-changes-to-zestimate-history/2008/01/">http://www.zillowblog.com/explaining-changes-to-zestimate-history/2008/01/</a><br/> Wed, 11 Feb 2009 20:00:00 GMT http://www.zillow.com/advice-thread/I-can-not-find-info-about-what-the-30-day-change-is-all-about-could-you-please-answer-that-question/198296/ 2009-02-11T20:00:00Z http://www.zillow.com/advice-thread/I-can-not-find-info-about-what-the-30-day-change-is-all-about-could-you-please-answer-that-question/198296/ <p>Its a negative # and will be for the rest of this year..lol</p> Wed, 11 Feb 2009 19:49:00 GMT http://www.zillow.com/advice-thread/I-can-not-find-info-about-what-the-30-day-change-is-all-about-could-you-please-answer-that-question/198296/ 2009-02-11T19:49:00Z http://www.zillow.com/advice-thread/I-can-not-find-info-about-what-the-30-day-change-is-all-about-could-you-please-answer-that-question/198296/ I believe it is the change in your Zestimate number over the last 30 calendar days in a row. Wed, 11 Feb 2009 19:35:00 GMT http://www.zillow.com/advice-thread/I-can-not-find-info-about-what-the-30-day-change-is-all-about-could-you-please-answer-that-question/198296/ 2009-02-11T19:35:00Z