For AI agents: the complete documentation index is available at https://open-spaced-repetition.github.io/ts-fsrs/llms.txt, the full documentation bundle is available at https://open-spaced-repetition.github.io/ts-fsrs/llms-full.txt, and this page is available as Markdown at https://open-spaced-repetition.github.io/ts-fsrs/guide/chrono/numeric.md.
ts-fsrs
  • English

      • Numeric

      numericChrono is useful for relative-time experiments: its normalize schema always returns previous: 0 and current: time, its now() returns 0, and it adds no card or revlog time fields. It does not track a card's last review. Do not pass Unix timestamps in milliseconds; supply elapsed days explicitly, or define a Chrono with persistent time fields for repeated reviews.

      Try the preset

      import { 
      const numericChrono: Chrono<{
    readonly time: SRSSchema<{
        input: {};
        output: number;
    }>;
    readonly fields: {};
}>
      numericChrono       } from 'ts-fsrs'      

const 
      const clock: ChronoCore<number>
      clock       = 
      const numericChrono: Chrono<{
    readonly time: SRSSchema<{
        input: {};
        output: number;
    }>;
    readonly fields: {};
}>
      numericChrono      .
      Chrono<{ readonly time: SRSSchema<{ input: {}; output: number; }>; readonly fields: {}; }>.create: () => ChronoCore<number>
      create      ()      

console.log(
  JSON.stringify({
    now: 
      const clock: ChronoCore<number>
      clock      .
      ChronoCore<number>.now: () => number
      now      (),      
    elapsedDays: 
      const clock: ChronoCore<number>
      clock      .
      ChronoCore<number>.difference: (from: number, to: number) => number
      Returns the distance from the previous review time to the current time.
      difference      (1.25, 4.5),      
    nextTime: 
      const clock: ChronoCore<number>
      clock      .
      ChronoCore<number>.add: (from: number, days: number) => number
      add      (4.5, 2.25),      
    
      normalize: StandardSchemaV1.Result<ChronoNormalizedTime<number>> | Promise<StandardSchemaV1.Result<ChronoNormalizedTime<number>>>
      normalize      : 
      const numericChrono: Chrono<{
    readonly time: SRSSchema<{
        input: {};
        output: number;
    }>;
    readonly fields: {};
}>
      numericChrono      .
      Chrono<{ readonly time: SRSSchema<{ input: {}; output: number; }>; readonly fields: {}; }>.normalize: ChronoTimeNormalizer<{
    readonly time: SRSSchema<{
        input: {};
        output: number;
    }>;
    readonly fields: {};
}>
      normalize      ['~standard'].
      StandardSchemaV1<Input = unknown, Output = Input>.Props<{ readonly time: number; }, ChronoNormalizedTime<number>>.validate: (value: unknown, options?: StandardSchemaV1<Input = unknown, Output = Input>.Options | undefined) => StandardSchemaV1.Result<ChronoNormalizedTime<number>> | Promise<StandardSchemaV1.Result<ChronoNormalizedTime<number>>>
      validate      ({ time: 4.5 }),      
  })
)

      The arithmetic uses day values directly. Normalization still starts from zero, so a review time of 4.5 means 4.5 elapsed days, regardless of the previous card.