Background: The health services literature indicates that the day and time of a medical encounter is often significant factor in patient outcomes, yet little is known about the role of temporal di-mensions in child maltreatment reporting or substantiation.Objective: We examined time-specific dynamics of screened-in reports of alleged maltreatment from different reporter sources, including their relationship to the likelihood of substantiation. Participants and setting: We used a population-based dataset of administrative records for 119,758 child protection investigations involving 193,300 unique children in Los Angeles County, Cali-fornia, between 2016 and 2017.Methods: For each report, we coded three categorical temporal dimensions of the maltreatment report: season, day of the week, and time of day. We descriptively examined how temporal characteristics varied by reporting source. Finally, we ran generalized linear models to estimate the likelihood of substantiation.Results: We observed variability overall and by reporter type for all three measures of time. Re-ports were less likely during summer months (22.2 %), during the weekend (13.6 %), and after midnight (10.4 %). Counts of reports from law enforcement were more common after midnight and contributed to a greater proportion of substantiations over the weekend than other reporter types. Weekend and morning reports were nearly 10 % more likely than weekday and afternoon to be substantiated, respectively. Reporter type was the most prominent factor for substantiation regardless of temporal dimensions.Conclusions: Screened-in reports varied by season and other classifications of time, but temporal dimensions exhibited only a modest influence on the likelihood of substantiation.