The rising participation of women in paid work has not only heightened demand for universal early education and care programs but also led to increased use of childcare amongst children at earlier ages. Prior research investigating Quebec's universal highly subsidized childcare documented significant declines in a variety of developmental outcomes for all children aged 0-4 years. However, past analysis has not explored whether these effects vary for children of different ages. In this article, we demonstrate substantial heterogeneity in policy impacts by child age. Children who gain access to subsidized childcare at earlier ages experience significantly larger negative impacts on developmental scores, health, and behavioral outcomes. The sole exception is the negative relationship between access to subsidized childcare and hyperactivity scores which steepens with child age. Our analysis additionally provides significant evidence of treatment effect heterogeneity within ages, and reveals benefits from access to universal childcare on developmental scores for those that are above 3 years of age. (author abstract)