It is defined in the TimeML Specification version 1.2.1[1] developed by several efforts, led 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.
[2] TimeML was conceptualized in 2002 during the TERQAS (Time and Event Recognition for Question Answering Systems) workshops, organized by Professor James Pustejovsky of Brandeis University.
The TARSQI (Temporal Awareness and Reasoning Systems for Question Interpretation) project currently develops algorithms that tag events and time expressions in natural language texts, anchor them temporally, and order them.
There were several changes made to the language, and are described in the version 1.2.1 TimeML guideline as such: ISO-TimeML was presented to the ISO for consideration as a standard in August 2007.
This subset of states includes those that are either transient or explicitly marked as participating in a temporal relation.
The TIMEX3 tag is primarily used to mark up explicit temporal expressions, such as times, dates, durations, etc.
TLINKS, or Temporal Links establish relationships between two or more events for the purpose of ordering them in time.