TimeTree is a public knowledge-base for information on the evolutionary timescale of life. A search utility allows exploration of the thousands of divergence times among organisms in the published literature. A tree-based (hierarchical) system is used to identify all published molecular time estimates bearing on the divergence of two chosen taxa, such as species, compute summary statistics, and present the results . . . For those interested in published summaries of relationships and divergence times of major groups of organisms (family level and above), see the authoritative synthesis The Timetree of Life.