I'm sure this kind of thing must be very common. My Mum's inability to make sense of time and date was what originally woke me up to her decline two years ago, and I've tried all sorts of things to keep her calm and cut down on frustrations. Nothing technological helps her, as a countdown on a screen means nothing to her, and I had to be there to set the timers anyway.
I've had some success making a 'bus clock' which is a cheap clock with the hour hand cut off and marker pen used to show when she needs to set off for the bus stop on a piece of paper attached to the dial. Another clock with the minute hand cut off can be used for appointments occurring once in the next 12 hours, but requires setting up in the morning.
Neither of these is any use whatsoever though if my Mum doesn't look at them... which is usually the case!
I've looked for hourglass type sand timers which could be used over an extended period, because it seems to me such a device is simpler to relate to. But there are limits to what's possible there, and again someone has to be there to make sure they're set up at the right time and can't be disturbed.
I've also experimented with a cheap laptop set up to a TV screen with a 'teleprompter' type display which changes throughout the day, telling Mum what channel she might enjoy on the TV at that time, whether she needs to do anything 'soon' or 'now' or 'later'. But it was a lot of effort to keep up to date and, again, she ignored it most of the time.
Ultimately I found it was less stressful for both of us if I just keep in touch regularly throughout the day to reassure Mum. But even now I'm only working part time and living with Mum for most of the week, managing her expectations about times and appointments can be... er, challenging. As the others say, the only practical solution is to keep quiet about appointments until necessary, but that doesn't work if it's a regular event they're aware is coming up and fret about all the time. Then it comes down to distraction and reassurance. If she'll listen! Sometimes all I can do is sit back, wait for things to get messy, and prepare to pick up the pieces.
Good luck.
