A treaty between the breakaway rebels, and the previous claimants to sovereignty, where the previous claimants accept the rebels claims and give up their own, would seem to be a pretty good candidate for the official start date of sovereignty.
The place where the treaty was signed is much less important than what it said and who signed it, even if it ends up being named after that place.
The place where the treaty was signed is much less important than what it said and who signed it, even if it ends up being named after that place.