How to customize the header using DataTemplate in WinUI Scheduler (Calendar)
In the WinUI Scheduler, customize the header using the HeaderTemplate property of the Scheduler.
XAML
The HeaderTemplate is defined for the Scheduler as shown in the following code sample.
<scheduler:SfScheduler x:Name="scheduler"
ViewType="Month"
>
<scheduler:SfScheduler.HeaderTemplate>
<DataTemplate >
<TextBlock
FontWeight="Bold"
Foreground="Blue"
FontSize="15"
FontFamily="fonts/bradhitc.ttf #Bradley Hand ITC"
Text="{Binding}" HorizontalAlignment='Stretch' VerticalAlignment="Stretch"/>
</DataTemplate>
</scheduler:SfScheduler.HeaderTemplate>
</scheduler:SfScheduler>

Take a moment to pursue the documentation. You can also find the options like customizing the scheduler header view.