Handheld devices owned by nomadic people can form intermittently connected mobile ad hoc networks spontaneously. Such networks appear as an attractive solution for service providers, such as local authorities, in order to extend a pre-existing infrastructure-based network composed of several infostations so as to provide nomadic people with application services in a large scale area (e.g., a city). In such hybrid networks, intermittent connections are prevalent, and end-toend paths between clients and providers cannot be maintained all the time. Service provisioning thus remains a challenging problem today in these networks. In this paper, we propose a new time-aware opportunistic routing protocol called TAO. TAO is designed for service invocation in intermittently connected hybrid networks. This protocol makes it possible to select the best next message forwarder(s) among a set of neighbor nodes based on the dates of contacts of these nodes with infostations, and tends to implicitly estimate the distance separating these mobile nodes and the infostations. This paper gives a detailed description of this protocol supported with some simulation results.