While we are waiting for Ken to do his magic...
Jachym, are these values based on a flat terrain? For example, I live in a valley with 9,000+ foot mountains all around me so the official calculated sunrise/sunset times are always many minutes off from what we experience locally. I don't expect any of the times to be accurate for all locations but, was wondering if the calculations are made for some kind of standard earth curvature value without terrain being a factor.