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# kABPersonAlternateBirthdayIsLeapMonthKey

The associated value is a <doc://com.apple.documentation/documentation/CoreFoundation/CFNumber> of type <doc://com.apple.documentation/documentation/CoreFoundation/CFNumberType/charType>.

```
let kABPersonAlternateBirthdayIsLeapMonthKey: CFString!
```

## Discussion

Used to represent a boolean—whose value is `true` if the birthday occurred during a leap month, `false` otherwise. Corresponds to <doc://com.apple.documentation/documentation/Foundation/NSDateComponents/isLeapMonth>.

---

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