## calculateAgeString() function

Calculates the age string for display using the age appropriate units. If the age is greater than or equal to 2 years, then the age is displayed in years. If the age is greater than or equal to 1 month, then the age is displayed in months. Otherwise, the age is displayed in days.

**Signature:**

```typescript
export declare function calculateAgeString(birthDateStr: string, endDateStr?: string): string | undefined;
```

## Parameters

| Parameter     | Type   | Description                                                          |
|---------------|--------|----------------------------------------------------------------------|
| birthDateStr  | string | The birth date or start date in ISO-8601 format YYYY-MM-DD.       |
| endDateStr    | string | _(Optional)_ Optional end date in ISO-8601 format YYYY-MM-DD. Default value is today. |

**Returns:**

string | undefined

The age string.