After years of trial and error, we've determined that the simplest way to change the clock in one of the in-built appliances in our kitchen is to kill its electrical power completely for a few minutes (by tripping the appropriate MCB in the consumer unit), then powering it back up.

When the power is restored, the appliance knows it's experienced a power cut, and asks for the current time.

Yes, this is completely ridiculous. No, I don't know why they designed the UI this way.