The nineteenth century was an era of rapid urban growth, increasing temporal awareness, and a rising demand for precision. Time measurement and display became particularly important in this context, not just for scientific or military purposes, but also for administrations, businesses and for the general public. There was, however, one significant problem: making all the public clocks show the same and correct time, which led to the development of urban temporal infrastructures as symbols of urban modernity and a source of civic pride. This article presents an account of the origins of two temporal infrastructures in Paris, focusing particularly on the electrical network devised by the scientists of the Paris Observatory.