Abstract: Transaction time is the time of a database transaction, i.e., an insertion, update, or deletion. A transaction- time database stores the transaction-time history of a database and supports transaction timeslice queries that retrieve past database states. This paper introduces transaction time to the World-wide Web. In a web context, transaction time is the modification time of a resource such as an XML document. A transaction-time web server archives resource versions and supports transaction timeslice. Unlike a database server, a web server is typically uninvolved in the update of a resource, instead it is only active when a resource is requested. This paper describes a lazy update protocol that enables a web server to manage resource versions during resource reads. An important benefit of our approach is that transaction-time can be supported by a transparent, minimal web server extension; no changes to legacy resources, HTTP, XML, or HTML are required. Furthermore, a web server can seamlessly become a transaction- time sever at any time without affecting or modifying the resources it services or other web servers.