This article presents a case study conducted in the metropolis of Brest, France in 2022, designed to support public policy decision-making by integrating the knowledge and needs of citizens during the different stages of a night-time urban planning project, around the notion of synchronization of the city’s rhythms. It presents three innovations: (1) Actors: coordination of public and private actors, common vocabulary, cartographic representations of assets, introduction of participatory approaches, activation of citizen knowledge in political expertise. (2) Sociology: participative modalities, objectification of citizens’ knowledge, definition of their decision-making perimeter, (3) Public lighting policies: territorial and social strategy of light sobriety, regularization and empowerment of the network of actors. The conclusion of this article will focus on the limits, added values and development axes of nocturnal urban sociology as a support for decision-making in public lighting management and renovation strategies, and will open up the mobilization of the rhythms and temporalities to be mobilized in order to restore balanced nocturnal ambiences between lighting, which is essential, and darkness, which is vital.