# Function: isDateInterval()

> **isDateInterval**(`matcher`): `matcher is DateInterval`

Returns true if `matcher` is of type [DateInterval](../type-aliases/DateInterval.md).

## Parameters

| Parameter | Type |
| :------ | :------ |
| `matcher` | `unknown` |

## Returns

`matcher is DateInterval`

## Source

[src/types/Matchers.ts:93](https://github.com/gpbl/react-day-picker/blob/9ad13dc72fff814dcf720a62f6e3b5ea38e8af6d/src/types/Matchers.ts#L93)