Feature Request: BCE dates

[apmireia]

Overview of the Feature Request
As mentioned in this discussion (https://groups.google.com/g/dataverse-community/c/Bj_dbHTeu2o/m/fFyyWfAsBAAJ), it would be interesting if Dataverse could support BCE (Before Common Era) dates. This functionality would greatly benefit datasets related to fields such as ancient history or archaeology.

What kind of user is the feature intended for?
API User, Curator, Depositor

What inspired the request?
We have several research centers that work with archaeological data.

What existing behavior do you want changed?
Allowing negative dates to be added, particularly in the 'time period covered' field, would be very useful.

[pdurbin]

@apmireia thanks for opening this issue.

BC dates are being discussed here:

• feat: index numerical and date fields in Solr with appropriate types + more targeted search result highlighting #10887

[vera]

To summarize the discussion in the PR linked by Phil:

Dataverse currently already supports the entry of dates in the format "yyyy BC" (it's just not documented):

dataverse/src/main/java/edu/harvard/iq/dataverse/DatasetFieldValueValidator.java

Lines 124 to 129 in d039a10

	if (!valid && value.getValue().contains("BC")) {
	testString = (testString.substring(0, testString.indexOf("BC"))).trim();
	if (StringUtils.isNumeric(testString)) {
	valid = true;
	}
	}

However, search capabilities for date fields in Dataverse are currently limited, because they are treated as text strings rather than dates.

Since the Solr search index underlying Dataverse supports BC dates (using the ISO 8601 format: 1 BC = +0000, 2 BC = -0001, and so on), I think we could add better search capabilities for BC dates relatively easily after #10887 is merged.