Date formats from Wikidata

[larsmic]

negative years(?) cause non-breaking errors by rdflib. They were queried from the wikidata graph.

Failed to convert Literal lexical form to value. Datatype=http://www.w3.org/2001/XMLSchema#dateTime, Converter=<function parse_datetime at 0x7fb9757ab910> Traceback (most recent call last): File "/usr/lib/python3.10/site-packages/rdflib/term.py", line 2084, in _castLexicalToPython return conv_func(lexical) # type: ignore[arg-type] File "/usr/lib/python3.10/site-packages/isodate/isodatetime.py", line 55, in parse_datetime tmpdate = parse_date(datestring) File "/usr/lib/python3.10/site-packages/isodate/isodates.py", line 203, in parse_date raise ISO8601Error('Unrecognised ISO 8601 date format: %r' % datestring) isodate.isoerror.ISO8601Error: Unrecognised ISO 8601 date format: '-0399-01-01'