story identification - 90s (or earlier) book/novel: daily memory loss and a device called the Memory

I've been trying to find the name of a book/novel that I read a few years back (although I think it was published in the 90s or earlier).

The main points that I remember are: the story is set in a future where humans have outlawed eating meat (among other things, possibly) due to its "animalistic" nature or something similar.

Everyone also has to follow this ritual of sorts at the end of every day where they drink a certain beverage (water mixed with crystals of some sort), which causes them to lose all memory of the previous day when they wake up the next day; the reason is something along the lines of forgetting the past and looking forward to the future.

If they stop this daily dose for a few days, they begin to regain all the memories they've lost due to the drink.

There's also this device called the Memory (if I remember correctly, that is), whose purpose I've unfortunately forgotten.

The protagonist is a boy, most probably a teenager. In the first part of the story, the protagonist observes how the time of the setting of the sun at dusk changes around the solstices. Later he befriends a girl of his age, but forgets her due to the daily memory loss.

The last part of the story had something to do with the protagonist and the girl being sent to a farm of sorts due to them not following the memory loss ritual.

And the ending... I wasn't able to understand what the ending was about at all when I read it, so I can't comment on that.

I've tried searching for this book with the information I have, but returned empty-handed.

Answer

The Vandal (1979) by Ann Schlee?

This review has the "individual Memory", rituals of memory loss, and the protagonist and a woman being sent in a colony for not following it:

This takes place in a Big Brother future where data to be preserved is stored in individual Memory banks and a daily Drink erases all real memories over three days old. In urgent, unconscious protest, teenage Paul sets a symbolic fire (light swallowing darkness); and as punishment the psychiatrist assigns him to Welfare work, caring for a sick woman in the substandards (housing units).

Meanwhile Paul begins to write himself secret notes and hide them, so that important experiences will not be lost. This is a serious offense. The sick woman is also having trouble with the pervasive system of memory repression.

Eventually she and, later, her daughter Sharon and Paul himself are sent into exile to a sort of prison colony, where people must work hard in the fields but, oddly, don't have to take the memory-erasing Drink. From there Paul and Sharon escape into the uncontrolled unknown, where some free spirits have preceded them and others are sure to follow.

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Found by searching this site for [story-identification] memory loss -[movie] -[short-stories] which brought up Dystopian future, an old novel where everyone only has a three day memory?.