Era of Time
A specified range of years that is named for an event, political ruler, or characterization of the timespan.
Eras are used in modern date representations of dates in, for example, Japan, Korea, China, and Vietnam. As an example, “2013” is in the Japanese era “昭和” (Heisei 25).
<!ELEMENT era (#PCDATA) >
Text, numbers, or special characters
... <date date-type="received" calendar="Japanese" iso-8601-date="2013-07-01"> <day>1</day> <month>7</month> <year>25</year> <era>昭和</era> </date> ...