Aktualität als erfolgskritischer Faktor bei Suchmaschinen [Up-to-dateness as a ranking factor in Web search engines]DirkLewandowskiauthorUp-to-dateness is an important factor for Web search engines in different aspects. Firstly, the web page index should be up to date, secondly, the use of date-restricted queries should be supported, and last but not least up-to-dateness is an important ranking factor. This article discusses the research findings in all three areas. The im-portance of the mentioned factors is stressed and it is shown that they are key for ranking web documents. Their importance will even increase with the age of the WWW.LS. Search engines.2006Preprint