> 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.

# 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

```ts twoslash file="../../../snippets/run-code/chrono-numeric.ts"
import { numericChrono } from 'ts-fsrs'

const clock = numericChrono.create()

console.log(
  JSON.stringify({
    now: clock.now(),
    elapsedDays: clock.difference(1.25, 4.5),
    nextTime: clock.add(4.5, 2.25),
    normalize: numericChrono.normalize['~standard'].validate({ time: 4.5 }),
  })
)

```


▶ Run code

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.