They do indeed seem to use the last time something significant was added to a building, which leads to strange dates such as a 19th building around the corner from where I live getting reported as 1983 because that, apparently, is when they added the hideously ugly front portal to it.
Strange thing is, they're inconsistent about it. De 1914 building De Vereeniging is listed as 1914 even though they've at the very least added a large conservatory to it since as well as a humongous - and very ugly and cheap looking - backstage area (though that was only this year, so maybe that hasn't ended up in the data set yet).
Strange thing is, they're inconsistent about it. De 1914 building De Vereeniging is listed as 1914 even though they've at the very least added a large conservatory to it since as well as a humongous - and very ugly and cheap looking - backstage area (though that was only this year, so maybe that hasn't ended up in the data set yet).
Oh well ...