# dateBefore

Source: https://smartassertions.dev/matchers/dateBefore/
Index of every page: https://smartassertions.dev/llms.txt

Matcher for a Date holding an instant earlier than the given one.

Matchers are applied through assertObjectMatches, where they narrow the corresponding property type.

## Usage

```ts
import { assertObjectMatches, dateBefore } from "@kensio/smartass";

const value: unknown = {
  createdAt: new Date("2026-01-01T00:00:00.000Z"),
};

assertObjectMatches(value, {
  createdAt: dateBefore(new Date("2026-06-01T00:00:00.000Z")),
});

// value is now narrowed to an object with a Date createdAt
// {
//   createdAt: Date;
// }
```

## Source

Source file: [`src/assert/date-before/date-before.match.ts`](https://github.com/KensioSoftware/smartass/blob/main/src/assert/date-before/date-before.match.ts)