Time use surveys are distinguished by their use of a specific type of questionnaire, the daily activity diary, first developed in the Soviet Union in the 1920s, standardized in the framework of a multinational survey headed by Alexander Szalai in 1965–66, then generalized for use in a great number of countries. The diary allows for quantifying the duration of relatively noninstitutionalized activities such as household work and leisure activities. The main research results obtained with time use studies are presented as they relate to three main themes: debates on the leisure civilization, changes in work rhythms, and gender roles and the synchronizing of social time within the family.