Could you post an example snippet from one of these files? You can iterate over the nodes with the tree methods find_clades() or get_nonterminals(), or search for the Event tags themselves with find_elements(PhyloXML.Events) -- assuming the information you want is in the "events" tag. But check the XML file or the documentation to confirm that this is the tag you want, and try playing with it in a Python interpreter (e.g. IPython, ipython-notebook) to see how to get the exact information you want.