Support BCE dates

[danfowler]

Overview

Supporting dates from before CE/AD requires something other than Python's default date-handling library. These dates would probable be specified as "negative" dates (e.g. https://en.wikipedia.org/wiki/ISO_8601#Years)

Originally: frictionlessdata/datapackage#386 (comment)

Pandas (via NumPy) supports BCE dates:

https://docs.scipy.org/doc/numpy/reference/arrays.datetime.html

Comes up in the context of the CMOA Collection data

@workergnome ...The non-castable value is going to be a problem—we do have to deal with dates BCE.

[roll]

Moved to the specs as it's doubtful that we can do it solely on the software level as standard date libraries don't support negative dates (so BCE is a new data type probably)

[cpina]

When thinking of support BCE dates: should we also think of supporting "circa" alike dates?: dates with uncertainty (person who was born in 1865-1867, or a specimen dated between V-VII century, etc.). I've seen archaeologists requesting this for some date fields in other systems and usually is overlooked.

Like "BCE dates" it might be another type of field and I don't know of any standard to describe these values. There are comments in schemaorg/suggestions-questions-brainstorming#219 and schema.org might have done some more work recently.

[roll]

It's definitely a topic for an extensive discussion 😃

[cpina]

When? some uncertain time in the future :-)
(sorry, I couldn't resist)

[rufuspollock]

This is not a specs items really - it is about how it is handled in a given language. I'd recommend closing this as INVALID or WONTFIX for now.

BTW if you want a library supporting BCE etc dates in python see this lib i wrote many years ago https://github.com/datopian/flexidate

[roll]

I agree theoretically it's an implementation level but in reality, it's not possible to support it in any of 10 language implementations without breaking changes unless there is a help from the specs like a allowBCE property or something.

I support closing it with a recommendation to use a string type and external libraries like flexidate to handle BCE dates. Although it can be moved to a forum; maybe some can suggest a good standard to rely on or something. Or provide more examples for the future.