The review history is stored in a tsv file, to avoid cluttering org files. This makes it easy to calculate review statistics.
- Date in ISO8601 format, second precision
- Card ID
- Ease (before review)
- Box (before review)
- Interval (before review)
- Seconds spent reviewing the card
- Repetition Spacing Algorithm used
More advanced review algorithms might need to use the review history of a card. In this case, the card ID + position should be used to look up the review history, as the filename can change when moving cards from file to file.