Wikipedia
TimeML
TimeML is a set of rules for encoding documents electronically. It is defined in the TimeML Specification version 1.2.1 developed by several efforts, lead in large part by the Laboratory for Linguistics and Computation at Brandeis University.
The TimeML project's goal is to create a standard markup language for temporal events in a document. TimeML addresses four problems regarding event markup, including time stamping (with which an event is anchored to a time), ordering events with respect to one another, reasoning with contextually underspecified temporal expressions, and reasoning about the length of events and their outcomes.