Abstract. Many online problems encountered in real-life involve a twostage decision process: upon arrival of a new request, an irrevocable firststage decision (the assignment of a specific resource to the request) must be made immediately, while in a second stage process, certain “subinstances” (that is, the instances of all requests assigned to a particular resource) can be solved to optimality (offline) later. We introduce the novel concept of an Online Target Date Assignment Problem (OnlineTDAP) as a general framework for online problems with this nature. Requests for the OnlineTDAP become known at certain dates. An online algorithm has to assign a target date to each request, specifying on which date the request should be processed (e. g., an appointment with a customer for a washing machine repair). The cost at a target date is given by the downstream cost, the optimal cost of processing all requests at that date w. r. t. some fixed downstream offline optimization problem (...