In 408/7 BC, the old Rhodian cities of Ialysus, Camirus, and Lindus united to form one polis and create a joint capital called Rhodes at the northern tip of the island. Cos, Cnidus, and other democratic or oligarchic cities followed their example more or less successfully in the course of the 4th century. They gave up their independence in favor of a superior and more distant sovereignty, sent out citizens to build up a new urban center, and therefore endangered the existence and identity of their old settlements for a prospective greater common goal. To constitute a sustainable union out of autonomous and rivaling poleis, their citizens – they are the protagonists – needed to establish sufficient public space where they could gather, dispute, and make terms: market places, theaters, courts and other buildings for political, administrative, legislative, economical and juridical interaction. Likewise they needed sacred space to share religious experiences: places, streets as well as sanctuaries of various kinds for celebrating and venerating the same gods and heroes. Both fields are the object of intense research, whereas much less attention has been paid to time as an important factor in this process. Reaching a consensus regarding the order and sequence of time is a prerequisite to collective identity, as I will argue, not only for synoecized poleis. The paper examines the introduction of the combined Rhodian calendar and its related new order of cults and festivals, in particular the installation of Helios as the principal god of the pan-Rhodian state, and the placement of the Helieia, his agonistic festival.