Spaced Repetition: How our review system works for flashcards in Retentium

A simple, science‑backed approach – optimized for everyday studying.

Reading time: ~3–4 min

Our system uses spaced repetition to help you remember more in less time. You study only the cards that are relevant today — new cards, cards with a past review date, and cards with a review date today — while easy cards get longer breaks between reviews.

How our schedule differs (simple and effective)

We use a streamlined, evidence‑aligned variant: first successful "Easy" → 4 days, then each subsequent "Easy" doubles the interval. If you press "Again", the interval resets to 1 day. This is easy to understand, fast to use, and consistent with the core principles behind the SM‑2 family of algorithms [5].

In practice: First "Easy" = 4 days → then 8, 16, 32… "Again" = back to 1 day.

What does "Today" mean?

"Today" is based on the calendar day. If you study at 23:58 and again at 00:02, a new day has started and cards with a review date on the new day become available. It's not a rolling 24‑hour period — it's midnight to midnight.

Which cards appear in "Today" mode?

New cards (no review date yet)
Past‑review‑date cards (review date in the past)
Cards with a review date today
Not suspended (suspended cards are hidden)

How is the next review calculated?

When you review a card you choose "Again" (hard) or "Easy" (easy):

Again: The interval resets to 1 day; the card appears again the next calendar day.
Easy: The first easy sets a 4‑day interval. Each subsequent easy doubles the interval (e.g., 4 → 8 → 16 days).

The next review date is calculated as today + interval (calendar days). This makes cards ready right at the start of the new day.

Why this aligns with the evidence: Distributed practice over time [1] and active retrieval [2] (actually recalling the answer) are core ingredients for stronger long‑term retention. For flashcards specifically, research shows distributed practice is more effective than cramming [3].

Example

You press "Easy" the first time → the card returns in 4 days.
You press "Easy" again next time → the interval doubles to 8 days.
If you later press "Again" → the interval resets to 1 day.

Why does this work?

Spaced repetition leverages how memory works: just before you forget [4], another review strengthens the memory the most [2]. By letting easy cards wait longer and hard cards return sooner, you maximize learning per minute [1].

Tips

Try to study a little every day so you clear today's queue.
If something feels difficult — choose "Again". It will return soon.
Aim for understanding in your answers, not just recognition.

Scientific backing (5 references)

Cepeda, N. J., Pashler, H., Vul, E., Wixted, J. T., & Rohrer, D. (2008). "Spacing effects in learning: A temporal ridgeline of optimal retention."Psychological Science, 19(11), 1095-1102. https://doi.org/10.1111/j.1467-9280.2008.02209.x
Karpicke, J. D., & Roediger, H. L. (2008). "The critical importance of retrieval for learning."Science, 319(5865), 966-968. https://doi.org/10.1126/science.1152408
Kornell, N. (2009). "Optimising learning using flashcards: Spacing is more effective than cramming."Applied Cognitive Psychology, 23(9), 1297-1317. https://doi.org/10.1002/acp.1537
Murre, J. M. J., & Dros, J. (2015). "Replication and analysis of Ebbinghaus' forgetting curve."PLOS ONE, 10(7), e0120644. https://doi.org/10.1371/journal.pone.0120644
Wozniak, P. A. (1990). "Optimization of learning" (SM‑2 algorithm, SuperMemo). https://www.supermemo.com/en/archives1990-2015/english/ol

Click on [1], [2], [3], [4], or [5] in the text above to see which reference supports each claim.

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