Sorry you can't find that page via the method I did, but just to keep a record this is what I did.
I clicked on Start on desktop and there is a list of items including Control Panel. I clicked that and got a panel headed "Adjust your computer's settings" with eight items in two columns, having four items in each column.
Item four in the first column is "Programs" with "Uninstall a program" in small blue coloured type underneath. I clicked the "Programs" link; not the "Uninstall" as both were usable but did different things.
I then got a panel with four items, and the third item is "Desktop Gadgets". Under that there are four links: "Add gadgets to the desktop" / "Get more gadgets online" / "Uninstall a gadget" / "Restore desktop gadgets installed with Windows". I tried to copy these panels to paste here but it would not do that.
I clicked "Get more gadgets online" and that's when I saw the page from Microsoft, headed "Gadgets have been discontinued". They go on to say why, being due to a security risk.
I did not dare to click on the "Uninstall a gadget" or the "Restore desktop gadgets installed with Windows". If you think I should click the "Restore" one then I will feel better about doing so, and will give it a try.
The heading "Desktop Gadgets" and the item under it "Add gadgets to the desktop" have a hand curser when hovered but they do not link anywhere. I have to go without my clock and calendar, it seems.
Sorry for going on so much, but there is no other way to show what I found and to explain it better.
The clock and the calendar have both re-appeared. I just turned my computer on and there they are. No idea why they went before, and no idea why they suddenly came back. Problem marked as solved again. Thanks for your help.