While social scientists have invested a lot of energy in exploring the uneven distribution of social groups in the city, they have surprisingly limited their efforts to investigating social segregation at the place of residence. The present paper investigates social segregation over the 24 hours a day in the Paris region, taking into account how social groups move within a city throughout the day. From a large and precise daily travel survey carried out in the Paris region (EGT 2010) among 25,500 respondents aged 16 or over, we have computed segregation indices and maps hour by hour from respondents' educational and socioprofessional indicators. We then observed that social segregation within the Paris region decreases during the day and that the most segregated group (the upper class group) during the night remains the most segregated during the day. We also explored how the co-presence between various social groups evolves throughout the day. Finally, we highlighted some large variations in districts' social composition over 24 hours: districts with similar social composition during the night can differ deeply in their social composition during the daytime because of socially selective daily trips. Exploring social segregation around the clock helps in considering more dynamically place effects on individual behavior and targeting areas to implement interventions more connected with the real city rhythm. Highlights-Segregation around the clock was explored from a travel survey (Paris region).-At city scale, social segregation is lower during the day than during the night.-The upper class is the most segregated group during the night and the day.-At local scale, large variations in districts' social composition occur over a day.-Daily trips which are socially and spatially selective alter maps of social groups.