Temporal expressions
A temporal expression in a text is a sequence of tokens (words, numbers and characters) that denote time, that is express a point in time, a duration or a frequency. Examples:

A point in time:He was born on <TIMEX>6 May, 1980</TIMEX>. A duration:The show lasted <TIMEX>7 minutes</TIMEX>. A frequency:The pump circulates the water <TIMEX>every 2 hours</TIMEX>. Initially, temporal expressions were considered a type of named entities and their identification was part of the named entity recognition task.