On April 6th, 2019, many GPSes, including TomTom, got hit be the "Millenium bug". Sort of. There's a 10 bit week number in the clock, and that means 1024 weeks, about 20 years. Who would have thought we'd be using GPS 20 years later? Duh.
The practical effect on my ancient TomTom XXL, is that it can no longer tell me how many minutes to go before reaching my destination, or what my speed is. This is a minor problem, but slightly annoying.
So I updated the TomTom software. That turned out to be non-trivial, of course. You can only do it from a Windows box or a Mac, so I downloaded the software, and tried to run it. It crached, of course. I tried again. Same result. So I loged in to the Windows box as root, and tried again. That worked, nd the software was installed. So I tried to run it, and it asked for my username and password, and it rejected the one I had written down, so I asked it to email me a pssword reminder. It emailed me a link to click on, except that I don't use a web interface to my email (it's just too dangerous). So I clicked on the link in the email, which showed me the URL, I copy-pasted the URL to Firefox, it asked for a new password, which I supplied.
Then I was able to run the update. I chose to also update the speed camera data, but it choked on that, so I left that out and re-ran, and it worked!
So now I have a map update, and the clock works again.