Very Interesting and suitable for special occasions, Not sure the abdication of a Danish queen is one for an international audience
A few engine runs appear to confirm it's unique but I'm not sure the engines are trustworthy in this. They might overlook alternatives until the mate is closer than 15 moves. I'll do some more testing.
Btw, players sometimes ask for advice on checkmating with K+Q vs K+B. Which is kind of silly when you see how helpless the bishops (of one color) are in an endgame like this one!
"15" days after it's declaration
I mirrored the position since the King's name will be Fredrick X
Therefore he stands on f10 spot (Remember Mr Myagi in "paint the fence" principal).