Date intervals

[gythaogg]

The django-interval field is useful to store fuzzy dates as intervals but it currently does not support BCE dates (acdh-oeaw/django-interval#23 ) as Python datetime fields do not support negative year (Guido van Rossum's comments here: https://discuss.python.org/t/bc-date-support/582).

1. Could we sort this out by saving the dates as integers? Is this going to be milliseconds elapsed from an epoch that we set?
2. In that case it would be necessary also to convert this to a human readable date format to show the actual range we are saving in the database
3. Sorting should work automatically based on the value of sort_date field if we choose integers. For filtering should we write our own methods?
4. Other formats potentially useful for storing BCE dates:
   • https://github.com/ixc/python-edtf (@richardhadden)
   • https://docs.astropy.org/en/stable/api/astropy.time.Time.html (possibly overkill)
   • what about Julian day as the date representation (integer) format - https://en.wikipedia.org/wiki/Julian_day It seems like it is robust enough for all kinds of dates in APIS (starts from January 1, 4713 BC)
   • Numpy as a datetime https://numpy.org/devdocs/reference/arrays.scalars.html#numpy.datetime64 that can store BCE dates (there's also pandas Timestamp and here's a fun chart connecting these formats: https://stackoverflow.com/questions/13703720/converting-between-datetime-timestamp-and-datetime64/21916253#21916253)

Lastly, it seems like python's calendar understands negative years - https://docs.python.org/3.12/library/calendar.html

Year 0 is 1 BC, year -1 is 2 BC, and so on.