1. A method of clustering documents for search results, the method comprising: accessing a database that is associated with a search engine, wherein the database includes a plurality of stored documents retrievable by the search engine; clustering some of the stored documents into one or more clusters based on content similarity; subdividing each of the one or more clusters into one or more subdivided clusters according to publication date; assigning an identifier to each of the clusters of the stored documents, wherein the identifier is assigned during a life span of each of the clustered stored documents, and wherein the identifier of each of the clusters remains persistent throughout the life span of each of the clustered stored documents; responsive to a search query, generating search results for presentation on a search results page, the search results comprising one or more of the subdivided clusters; and presenting the search results on the search result page, wherein each subdivided cluster presented on the search results page includes a synopsis of the subdivided cluster and links to documents contained within the subdivided cluster.