Uncertain dates

Schema: EAC-CPF 2.0

Context: Encoding uncertain dates in <date>, <toDate>, <fromDate>

Description: The attributes @certainty, @notBefore and @notAfter can be used with the <date>, <toDate>, <fromDate> elements to express the level of certainty of a particular date. @notBefore and @notAfter can be used to indicate the earliest and latest possible dates that an uncertain date might fall between. @certainty can be used to encode a term such as approximate, circa, or uncertain to indicate the level of certainty of the date provided. The @calendar and @era attributes are also available to provide additional information about a date.

EAC-CPF will also enable the use of the Extended Date/Time Format (EDTF), which has been included in the latest version of the ISO 8601 standard. This allows for the encoding of dates as ‘uncertain’ (?), ‘approximate’ (~), and ‘uncertain and approximate’ (%) within the machine-processable date in the @standardDate attribute for <date>, <fromDate> and <toDate>.

Example

<dateRange>
	<fromDate notBefore="1971" notAfter="1975">around 1973</fromdate>
	<toDate standardDate="1992">1992</toDate>
</dateRange>

<date certainty="uncertain" standardDate="1968?">circa 1968</date> 

<date notBefore="1701">not before the 18th century</date>

<dateRange>
	<fromDate notBefore="1720">not before the 1720s</fromDate>
	<toDate notAfter="1759">not after the 1750s</toDate>
</dateRange>

<dateRange>
	<fromDate calendar="gregorian" certainty="approximate" era="ce" standardDate="1950">1950</fromDate>
	<toDate calendar="gregorian" certainty="approximate" era="ce" standardDate="2000">2000</toDate>
</dateRange>