# fdu

> An ultra-fast, zero-dependency date-time library for JavaScript. It runs about 4 times faster than Day.js.

An ultra-fast, zero-dependency date-time library for JavaScript and TypeScript. It has an immutable API, a tree-shakeable ESM design, and locale-aware formatting. Its arithmetic follows calendar-correct floor semantics, meaning it rounds date math down to whole units instead of up.

## Performance

fdu was benchmarked against [Day.js](https://day.js.org/), [date-fns](https://date-fns.org/), and [Luxon](https://moment.github.io/luxon/). The results:

- fdu runs 4 times faster at date manipulation.
- fdu runs 13 times faster at comparisons.
- fdu runs 1.7 times faster at formatting.

## Usage

```typescript
import { fdu } from "@pyyupsk/fdu";

const date = fdu("2025-09-30");

date.format("YYYY-MM-DD HH:mm:ss");
date.add(1, "day").format("[Tomorrow is] dddd");
```