Currently, card reviews appear to be scheduled at exact 24-hour intervals from when they were last reviewed. For example, if I review a card at 9 PM, it will only become available again at 9 PM on future review dates, not earlier in the day.
This creates an inconvenient workflow where cards become available throughout the day rather than in one complete batch. If I do a morning study session and check again in the evening, additional cards have appeared.
Anki solves this by making all cards for a given date available at a set time (like midnight or 2 AM), allowing users to batch all their reviews together instead of chasing them throughout the day.
I suggest changing the review system so that all cards scheduled for a date become available at midnight (or provide a user preference for when the “new day” begins, such as 2 AM or 6 AM). This would enable more efficient batch studying rather than forcing users to check multiple times per day or let cards carry over.
Ideally, you’d want to review each card right before you’d forget its content. The authors of spaced repetition software face two challenges - we don’t know when is the right moment, and the users will not review the cards right at the scheduled moment but typically later.
It’s clear that if you regularly revise later than the ideal interval, you forget more of the cards and therefore you spend more time re-learning forgotten cards.
However, if you regularly revise earlier than ideal, you also spend more time revising, because you keep strengthening memories that were still strong enough.
Therefore, assuming the ideal interval was 24 hours, there’s no reason to prefer revising after 12 hours (earlier on the same day) to revising after 36 or even 48 hours (one day later). Both ways are a little bit suboptimal and neither is too bad for you. Moreover, the planning algorithm already knows that you’re likely to actually revise somewhat later than when it schedules the card, so it is taken into account.
I think it’s also good to realize that ReadLang makes sure that you review the most frequent words first, so if you accummulate too many cards in the queue, you can simply leave them there; you’re not expected to empty your queue daily, and it’s perfectly ok to never empty it! Some of the words will come up later, after you master the frequent words, and the least frequent words will stay in the queue forever, which is ok - you do not need to master them.
maybe one needs to introduce another category, with a button like “Ask me next time again”… independent of when that will be 
depending on the users’ schedule.
Hi Anna, thanks for the nice, detailed reply. I understand and appreciate your points. With over 20,000 cards studied and learned on Anki over the past 3.5 years, and 5,000 cards on Readlang in the past year, I am a bit familiar with SRS and timing. Yes, I have read all the nerd stuff, including the latest FSRS by Anki. I also know that a difference of 24 hours or 12 hours is completely insignificant in the long term. That is why Anki SRS varies the dates at longer intervals, so cards don’t pile up on the same day and to even out spacing. There is an optimum window. The importance of exactness in the first few days of learning doesn’t make a long-term difference, not a bit. The importance things are making good cards, understanding them rather than just memorizing, and then doing the reps long term.
My suggestion has nothing to do with the overall algorithm or its optimization. My suggestion is that all cards planned for that day become available at midnight, like in the biggest and most experienced program, Anki, used by medical students and grad students. Depending on my day, I may study before lunch, or maybe I study after dinner, or maybe I review throughout the day. The difference between studying a card at 10 a.m. versus 6 p.m. is non-existent in the long term. But I cannot get all my cards done at 10 a.m. because Readlang says I have to wait until 6 p.m. to review cards that I reviewed 270 days ago at 6 p.m. Obviously, our memories will not be impacted by studying those cards earlier than, for example, the exact 270×24 hours to the exact 6,480 hours, which is what is going on now.
Again, I am simply requesting that all cards for the upcoming day become available to review at midnight.
For the long-term cards, what harm comes from practicing at 10 a.m. and not seeing the cards that are scheduled for 6 p.m. until the next day?