# Custom Interval Types

`RadTimeBar` provides built-in support for a couple of predefined interval types ranging from milliseconds to centuries. For a full list of the predefined intervals, please refer to the [Interval Formatters](https://www.telerik.com/winui/documentation/controls/radtimebar/intervals-formatter) article. For all custom scenarios that the predefined intervals do not cover, the control supports custom interval type implementations.

## Using Custom Interval Types

The `Intervals` collection contains items of type `IntervalBase`. That is why, in order to configure a RadTimeBar control to use a custom interval type, simply add an instance of that custom interval to the Intervals collection of the control.

The example below shows how you can add a custom interval type to the Intervals collection of a RadTimeBar control:

#### **Adding a custom Interval to the Intervals collection of RadTimeBar**

```XAML
<telerik:RadTimeBar.Intervals>
	<example:CustomInterval />
	<telerik:MonthInterval />
</telerik:RadTimeBar.Intervals>
```

## The IntervalBase class

A custom interval is a class that inherits the `IntervalBase` class and implements its abstract properties and methods:

* `Formatters`—Gets a collection of formatter that the interval can use to convert **DateTime** objects to strings.
* `MinimumPeriodLength`—Gets the smallest interval period.
* `ExtractIntervalStart`—Given a **DateTime** object, this method returns the start of the interval that contains the given DateTime object.
* `IncrementByInterval`—Given a **DateTime** object and span, this method increments the specified DateTime object by the specified number of `MinimumPeriodLengths` property.

Below you can find a sample custom interval implementation:

#### **Creating a custom Interval**

```C#
public class CustomInterval : IntervalBase
{
	private static readonly Func<DateTime, string>[] formatters;

	static CustomInterval()
	{
		formatters = new Func<DateTime, string>[]
		{
			date => string.Format("My custom interval {0}, {1}", GetNumberOfInterval(date), date.ToString("yyyy")),
			date => string.Format("Custom interval {0}", GetNumberOfInterval(date)),
			date => string.Format("C{0} {1}", GetNumberOfInterval(date), date.ToString("yyyy")),
		};
	}

	public override DateTime ExtractIntervalStart(DateTime date)
	{
		int firstMonthOfInterval = GetFirstMonthOfInterval(date);
		return new DateTime(date.Year, firstMonthOfInterval, 1);
	}

	public override DateTime IncrementByInterval(DateTime date, int intervalSpan)
	{
		return date.AddMonths(intervalSpan * 6);
	}

	public override Func<DateTime, string>[] Formatters
	{
		get
		{
			return formatters;
		}
	}

	public override TimeSpan MinimumPeriodLength
	{
		get
		{
			return TimeSpan.FromDays(180);
		}
	}

	private static int GetNumberOfInterval(DateTime date)
	{
		int number = ((date.Month - 1) / 6) + 1;
		return number;
	}

	private int GetFirstMonthOfInterval(DateTime date)
	{
		int quarter = GetNumberOfInterval(date);
		int firstMonthOfInterval = ((quarter - 1) * 6) + 1;
		return firstMonthOfInterval;
	}
}
```

**RadTimeBar with custom Interval**

![RadTimebar with custom Interval](https://www.telerik.com/winui/documentation/assets/9b7c1a150c0e853c18b9484324ca683e/radtimebar-custom-interval-types-0.png)

## See Also

* [Intervals Formatters](https://www.telerik.com/winui/documentation/controls/radtimebar/intervals-formatter)
* [Formatter Provider](https://www.telerik.com/winui/documentation/controls/radtimebar/formatter-provider)