1. A method implemented by data processing apparatus, the method comprising: identifying an entity based on entity text included in document text of a document; identifying a time-sensitive attribute for the entity based on attribute text included in the document text; identifying a first value for the time-sensitive attribute based on value text included in the document text; generating a query specifying the entity; providing the query to a search system that provides a result value for the time-sensitive attribute of the entity included in the query; and providing, to a user device that is currently accessing the document, result data that causes presentation of the result value as a replacement for the first value.