In this proposed study we investigate how much neighborhoods of different racial/ethnic arrangements become more or less diverse during the day. We then aim to assess possible explanations for differences in these dynamics across neighborhoods and metropolitan areas. Current results highlight a substantial degree of intraday neighborhood change, but also underscore its conditional nature. Analyses of data from the Census Transportation Planning Package show that, on the margins, nearly all intraday diversification of substantial magnitude is attributable to increased contact between persons of different racial and ethnic backgrounds within neighborhoods that have multiethnic or majority non-White nighttime residential populations. The results of this study stand to contribute important insights about how many individuals' daily mobility patterns cross the residential boundaries that otherwise separate social life at night, though existing patterns of segregation nonetheless reverberate through commuting flows that connect one largely segregated area to another.