Evolutionary timescales can be estimated from DNA sequence data using the molecular clock, a statistical model that describes the behaviour of evolutionary rates among organisms. Although originally based on the assumption of rate constancy among lineages, molecular clocks now include ‘relaxed’ variants that are able to accommodate heterogeneous rates. These have provided useful insights into evolutionary rates and timescales across the Tree of Life.

Genome-scale data offer exciting opportunities for improving our understanding of molecular evolution and refining our estimates of evolutionary timescales. However, they also bring considerable computational and analytical challenges. I describe some of the approaches that have been used to estimate evolutionary timescales from genome-scale data. I focus on two recent examples, one concerning the diversification of birds and the other concerning the evolutionary dynamics of potato blight fungus. I also speculate on the future of molecular clocks, describing the key limitations and highlighting some of the most promising research directions.