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# init(start:duration:)

Initializes a date interval with a given start date and duration.

```
init(start startDate: Date, duration: TimeInterval)
```

## Parameters

`startDate`

The start date of the date interval.

`duration`

The duration from the start date for the date interval.
  
  > Important:
  > This method raises an `NSArgumentException` if ``doc://com.apple.foundation/documentation/Foundation/NSDateInterval/duration`` is less than `0`.

## Discussion

This is the designated initializer.

---

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