The assessment of the vulnerability of urban population to potential natural and man-made hazards is hampered by the high intensity of intracity movements of residents and the uneven daily distribution of the population across the urbanized territory. This factor of uncertainty creates a problem with the allocation of funds and resources needed to mitigate risks. Different urban areas have different daily profile of changes in their population. This paper presents an original methodological approach to the dynamic assessment of the population of urban areas based on the fragmentation of the day into temporary elements of “social time” - pacemakers: determining the functional affiliation of “day” and “night”, and the nature of intraday dynamics - “morning start” and “evening finish”. Reliance on a highly detailed array of anonymized data from mobile operators on the localization of subscribers and an analysis of the urban space of Moscow through the prism of social time made it possible to improve the accuracy of estimates of the actual population of intracity territories, linking them to objectively existing time intervals. The authors identify 14 types of municipalities and formulate recommendations to reduce the population’s vulnerability to emergency situations.