Over the last two decades, technologies available to children have accelerated with the advent of wireless internet and increasing portability and affordability of electronic devices. Children's technology use is a rapidly evolving challenge for families, organizing their everyday lives and potentially resulting in social disparities in technology use and displacement of healthy behaviors. This study examined time spent on technology use, physical activity, play, and sleep by US children across early (ages 2-5) and middle (ages 6-11) childhood in two cohorts using time diary data with a focus on variation by class and race. Data came from the Panel Study of Income Dynamics Child Development Supplement in 1997 (N = 2193) and 2014-2016 (N = 1009). Multivariate regression models estimated total time spent engaged in technology use, physical activity, unstructured play, and sleep. Total time spent engaged with technology increased 32% since 1997 in early childhood and 23% in middle childhood. Technology use was lowest for children with the most highly educated parents. In the more recent cohort, technology use was associated with displacement of physical activity in middle childhood but with increased play in early childhood and increased sleep in middle childhood. Results suggest that changes over time in technology use have restructured children's everyday lives in ways that may be consequential for health and development, but co-occurring declines in physical activity and unstructured play cannot be attributed solely to technology time.