Molecular dating of phylogenetic trees is a growing discipline using sequence data to co-estimate the timing of evolutionary events with rates of molecular evolution. Ail molecular-dating methods require converting genetic divergence between sequences into absolute time. Historically, this could only be achieved by associating externally derived dates obtained from fossil or biogeographical evidence to internal nodes of the tree. In some cases, notably for fast-evolving organisms such as viruses and some bacteria, the timespan over which samples were collected may cover a significant proportion of the time since they last shared a common ancestor. This situation allows phylogenetic trees to be calibrated by associating sampling dates directly to the sequences representing the tips of the tree. The increasing availability of genomic data from ancient DNA extends the applicability of such tip-based calibration to a new panel of organisms for which fossil data are rarely available. In this talk, 1 will introduce the rationale for performing tip-dating inferences, review some recent applications in a variety of organisms and discuss the prospect of carrying out such analyses in plantpathogenic bacteria systems.