When it happens
Late in mild stage but consistently in moderate-stage dementia
Why it happens
As recent memory erodes, it becomes harder to store (and therefore retrieve) memories of events that just took place. First routine events are forgotten easily, such as what one ate; then even big events, such as a special outing, fail to be recorded in the brain. Disorientation regarding time and place also make it harder to recollect. Exception: Events with a strong emotional component may be retained longer.
What you can do
Don't stop creating special moments just because they're quickly forgotten. Meals out, visits from friends and family, outings to favorite places all continue to help someone with dementia feel valued and loved and to have a sense of belonging.
Try not to quiz: "Do you remember what we did yesterday?" That puts the person on the defensive. Better to just dive into talking about the event. (The person may recall it, may pretend to recall if even if he or she doesn't, or simply enjoy hearing or talking about it.)
Remember that the quality of the event or the level of enjoyment has little relationship to whether it's remembered. But the good mood that a great day brings can stick with the person for days afterward.