It seems that changing when the next day starts can mess up with the functioning of FSRS. I used to do that a lot (and I mean a lot, like every day). I have found other people who do that when I opened this issue in AnkiDroid’s repo.
Here is what Expertium had to say about it:[Emphasis mine] “Next day starts at” (and also timezone info) is necessary to determine when reviews happened and which reviews happened on the same day.
If you change it a lot, or if you travel a lot (which changes time zones), it can change what FSRS sees as “same-day reviews”.
Now he also thinks this (probably, he says) wouldn’t be too damaging but I’d still say users getting this info in-app would be good. Personally I wouldn’t risk playing around with if it as if it were my personal time-machine.
There is a warning that says ‘custom scheduling’ version of FSRS should be cleared up before enabling FSRS in Anki. I think what I suggest can be added at the end as sort of an annexure similarly.
No harm in adding. The fact that I found two other users doing that (in GitHub) was shocking in itself. At least I’m sure that people do it when faced with backlog. Whether it’s 9 percent users or 18 percent shouldn’t be an issue (IMO).
Actually consider this, how many people are using ‘custom scheduling’ version of FSRS? We still have a warning about that. Actually most people even a few months ago were unaware of what FSRS is. Most people I talk to at least.
The cost of adding another warning is a few lines and some time and effort. The former can be solved by removing the warning about ‘custom scheduling’ version because pretty sure the few people using it have switched over.
I wouldn’t be pushing back if I thought that this was more common than users coming from the custom scheduling version of FSRS. Changing next day starts at also impacts the calendar in the graphs, so I’d think frequent users of that feature would already be aware of this. If anything, a warning probably belongs in the documentation for that option, not in the FSRS docs.
This doesn’t seem unique to FSRS, so I don’t think an FSRS-specific warning is necessary. Changing day/date/time-zone has always impacted scheduling because it is primarily fixed to a continuous clock/calendar. If you move yourself within that clock/calendar, the schedule changes. But if you move yourself back, the schedule changes back. It’s the same functionality that results in gaps in Heatmap that come and go with time changes (DST, travel).
It’s possible that the specific issues that you and briankrznarich were attempting to document (card limits, undo, etc.) need fixes, but I’m not seeing a general issue of “changing next day impacts FSRS.”
As far as a general warning in the docs – It’s not clear to me what the goal of that next-day changing was, or if it actually accomplished anything. It’s hard to imagine that a very many users are playing those sort of games with their scheduling if it doesn’t have an effect.
For instance, if you push the next-day time forward, to get more time in “today” to finish your reviews, and then you push it back, the record of those reviews moves to the next day. Those reviews switch to the other side of the day boundary and there’s no permanent record of it in your collection.
I agree with this. I actually didn’t know that this option messes up with statistics and can do the same for FSRS so this info should be there IMO (yes I don’t look at heatmaps etc).
Well, that’s the point I was getting at – fussing with the day-start doesn’t save you from anything because all of the cards coming due are still coming due. If you have 100 cards that will be due when the “next” day starts at 4am, and you move that time to 6am – those same 100 cards will be due at 6am. Since it is not actually a time-machine (as you put it), it doesn’t change anything.
No but I will be doing the reviews then and If I haven’t even slept the night I wouldn’t want those cards to get due. It’s not really me changing when next day starts and then going to sleep.
Edit: I think I’m putting this the wrong way. We’re not saving ourselves from backlog really. The issue’s more like undone reviews. You have 100 cards to do today and while you’re doing it the deadline (next day) comes close so you push new day to the future. I would sometimes have to change it to 6:00 am from 4:00 am and then if cant complete my cards I’d change it to 9:00 am. The problem was my large backlog yes but a better way of putting it is not being able to finish my cards before going to sleep (my sleep schedule got messed up because of that; I was going to sleep around 8 am in the morning)
All I’m getting is that this is “fear of a backlog”-based self-trickery. What you’re doing doesn’t produce any practical or lasting impact – it just makes you feel better that day. Of course, you’re free to do it if you like, but this is what makes me think it’s not a common behavior, and doesn’t need to be specifically flagged/warned-about.
