I got one for my wife about 2 years ago. It shows the day and time in large characters and then the full date (dd mmm yyyy) in small characters. I put it in the kitchen next to the calendar as she was always looking at that to find out the day, and usually getting it wrong. I also stopped writing future events onto the calendar as this just encouraged her to stress about things that might not be happening for weeks. I thought that these actions might help her work out the day and time and preserve a bit of independence.
The clock has been of limited use as, even if she looks at it, she appears not to take in what it says. For example, if she is reading the TV listings and I notice that she is on the wrong day it is only when I direct her attention to the day clock that she seems to realise that it is there and has the basic information that she needs.
The clock also has an annoying quirk, despite having a battery backup which is supposed to power a 'memory'. Several times a week I notice that the time on the clock is wrong by several hours (always behind), as though it has stopped for a while then restarted without resetting the time correctly. I have even seen it go blank and come back on with the wrong time. I suspect that it may be sensitive to power spikes or other variations.
Switching off and back on at the socket always puts this right but I have started to think that an Alzheimer's clock that itself can't remember the time is maybe more trouble than it is worth.