dates should be supported that are before christ was born (Ie. negative dates!)

[TMeerhof]

because there will be archeological data in the API, we should support dates BC.
Python datatime has no support for these dates.

[breyten]

I toyed a little with this:

import datetime

class DateBC(datetime.date):
    bc = False
    def __str__(self):
        prefix = '-' if self.bc else ''
        return u'%s%s' % (prefix, super(DateDC, self).__str__(),)

Which works if you set the bc attribute to True. Modifying isoformat() would probably work the same way and then all we need to know is if these negative dates are supported by Elasticsearch.

We can do this trick because we're not calculating with dates anyway.

(I'll check for Elasticsearch support)