Whiteboard: u=dev c=backend p=0
I have studied this problem yesterday, and IMHO there is an issue with editing blurred dates. First think to know is that it is possible to edit precisions of dates (precision, before after,...) with a bot and to access to those data in json or xml. A very good point. But
On the interface we cannot see those precisions of a date and manually bad correction can be done. Furthermore we can have the same restitution for different dates. Written "1150" precision "century", "12.century" is displayed. Written "12.century", "12. century". But data stored are diffrent : 1150, precision 7 and 1200 precision 7 for the second. There is a risk that, as contributors, we are curently editing a date in different ways for a same value. If we read the model description "1580" precision "decade" means a decade precision on a date from a year (minus or plus), which is a different interval of the "1580s" displayed (maybe am I wrong on this point). Another problem is that some contributors use P580-start date and P581-end date.
Finally blurred dates that we are currently editing are not homogeneous and we can not neither see or correct them on the interface. A solution for a good editing blurred date with the data_type model would be great. I hope these comments could be helpful.