Reconstructing the timescale of the Tree of Life is one of the principal aims of evolutionary biology. This has been greatly aided by the development of the molecular clock, which enables evolutionary timescales to be estimated from genetic data. In recent years, high-throughput sequencing technology has led to an increase in the feasibility and availability of genome-scale data sets. These represent a rich source of biological information, but they also bring a set of analytical challenges. In this review, we provide an overview of phylogenomic dating and describe the challenges associated with analysing genome-scale data. We also report on recent phylogenomic estimates of the evolutionary timescales of mammals, birds, and insects.