Spaced repetition is a learning technique that involves reviewing information at increasing intervals. Based on the forgetting curve discovered by Hermann Ebbinghaus in 1885, it combats memory decay by strategically timing reviews just before you're likely to forget. This strengthens neural pathways and moves information from short-term to long-term memory more effectively than traditional study methods.

The optimal review frequency depends on your learning goals and timeline. For general learning: Day 1, 2, 4, 7, 15, 30. For exam preparation: Day 1, 2, 3, 5, 8, 12. For rehabilitation: Day 1, 1, 2, 3, 5, 7. WhenToReview automatically calculates the best intervals based on your specific scenario using 5 scientific algorithms.

Research shows different optimal intervals for different scenarios: Ebbinghaus Classic (1, 2, 4, 7, 15, 30 days) works best for general learning. Cepeda's 2008 Science study found shorter intervals (1, 2, 3, 5, 8, 12 days) optimal for exam preparation. SuperMemo's adaptive intervals adjust based on difficulty. WhenToReview automatically selects the research-backed intervals for your specific use case.

The best algorithm depends on your learning scenario: Ebbinghaus for general learning, SuperMemo SM-2 for long-term retention, Cepeda Optimal for exam preparation, Cognitive Load for rehabilitation, Adaptive Hybrid for mixed content. Instead of choosing manually, WhenToReview automatically selects the optimal algorithm based on your content type and timeline.

Single-algorithm tools like Anki (SuperMemo only) or Quizlet (basic repetition) aren't optimized for all scenarios. Multi-algorithm selection provides: 90-95% retention for exam prep (Cepeda), 85-95% for long-term learning (SuperMemo), 70-80% for rehabilitation (Cognitive Load). WhenToReview combines 140 years of research into one intelligent system.

WhenToReview exports universal ICS files compatible with all major calendar applications: Google Calendar, Apple Calendar, Outlook, Teams, Notion, DingTalk, Feishu, and any app supporting ICS format. The system automatically sets 3-layer reminders (15 minutes, 1 hour, 1 day before) for optimal review timing.

Spaced repetition is highly effective for medical education, with studies showing 85-95% retention rates for anatomy, pharmacology, and clinical procedures. Medical students benefit from: Cepeda intervals for board exam preparation, SuperMemo for long-term knowledge retention, Cognitive Load optimization for complex procedures. WhenToReview automatically optimizes for medical learning scenarios.

Language learning benefits from different algorithms for different components: Vocabulary acquisition uses Ebbinghaus intervals (1, 2, 4, 7, 15, 30 days), Grammar patterns use SuperMemo adaptive intervals, Pronunciation practice uses shorter Cepeda intervals. WhenToReview automatically selects the optimal algorithm based on your language learning content type.

Yes, spaced repetition is effective for cognitive rehabilitation, using Cognitive Load Theory to minimize mental strain while maximizing retention. Rehabilitation schedules use gentler intervals (1, 1, 2, 3, 5, 7 days) with lower cognitive load. WhenToReview's rehabilitation preset is specifically designed for patients recovering from brain injury, stroke, or age-related cognitive decline.

Certification exam preparation benefits from Cepeda's optimal intervals research, which found shorter, more frequent reviews (1, 2, 3, 5, 8, 12 days) maximize retention for time-constrained goals. This approach achieves 90-95% retention rates for professional certifications like CPA, PMP, AWS, Google Cloud, and medical board exams.