[RobboEdin]

You need to look very carefully.
On my old iPad Mini, the box to change date is completely white so it’s easy to see, at the top, The Now and Done button.
However, on my new iPad, running the latest iOS, it’s less obvious as, to the top of the white box, the Now and Done are in a box which is almost the same colour as the background.
If I knew how to attach a screenshot, I’d show you but suggest you press to the top right of the date change box.