How spaced repetition scheduling works
In 1885, Hermann Ebbinghaus mapped the forgetting curve: without review, most of what you learn today is gone within a week. But each time you successfully recall something just before forgetting it, the curve flattens — the memory lasts longer. Spaced repetition turns that into a schedule: review at expanding intervals, so every session lands at the moment of maximum benefit.
This calculator uses the classic expanding ladder — reviews 1, 3, 7, 16 and 35 days after first learning — or a custom multiplier if you want gentler or steeper spacing. Enter the date you learned the material and you get five concrete calendar dates. Download them as an .ics file and your phone will remind you; the whole point of spacing is that the fourth review only works if you actually show up for it.
How to use the review dates well
At each review, close the book first. Try to recall the material from memory — explain it aloud, sketch it, or answer practice questions — and only then check what you missed. That act of effortful retrieval, not the re-reading afterwards, is what strengthens the memory. A review session can be short: ten focused minutes per topic is usually enough. If a review feels shaky, treat it as day zero again and restart the ladder for that topic; if it feels effortless, you can safely skip to a longer gap.
Spacing tells you when to study, but not what or how. If you're planning a bigger goal — an exam, a language level, a new skill — a schedule of review dates is only one layer. PlanAny generates the full stack: a day-by-day plan, real lessons for each step, and a Socratic check that you actually understood before you move on.