As The Crown is sovereign of the United Kingdom, is this running in Buckingham Palace or in City of London?

Can the user choose which sovereign is doing the computation?

I'd personally prefer not to have the weird uncle do the computation, maybe the younger ones living abroad can do it.

;)

Parliamentary sovereignty is a cornerstone of the UK constitution, fwiw. Parliament has been de facto sovereign since the late 1600s.

The server is under the woolsack!