How to sort a Listview in a DataTemplate in XAML only?

Question

I have a window with a TabControl that i've bind to a list of objec, I'll called MyItem :

    <TabControl Name="MyTabPNL"  Background="Gainsboro"
        ItemsSource="{Binding MyItemList, ElementName=WatcherWindow}"
        ContentTemplate="{StaticResource tabItemTemplate}">
    </TabControl>

This MyItem class has an ObservableCollection, that I want to bind to a Listview, I'm doing this with a DataTemplate. GOAL: I'd like to sort automatically this ObservableCollection in XAML. Usually i would use a CollectionViewSource, but i can't find a way to this... I've tried stuff like that:

<DataTemplate x:Key="tabItemTemplate">
        <DataTemplate.Resources> 
            <CollectionViewSource x:Key='dayList' Source="{Binding MyDayList}">
                <CollectionViewSource.SortDescriptions>
                    <scm:SortDescription PropertyName="MyDate" Direction="Descending"  />
                </CollectionViewSource.SortDescriptions>
            </CollectionViewSource>
        </DataTemplate.Resources>

    <Grid >
         <ListView ItemsSource="{Binding Source={StaticResource dayList}}" >
            <ListView.View>
                <GridView x:Name="gridvwDay" >
                    <GridViewColumn Header="MyDate" 
                          CellTemplate="{StaticResource myCellTemplatePNLDate}"
                          HeaderContainerStyle="{StaticResource CustomHeaderStyleNeutral}" 
                           Width="70" />
                </GridView>
            </ListView.View>
        </ListView>
   </Grid>

But everytime i've got the same error:

System.Windows.Data Error: 2 : Cannot find governing FrameworkElement or FrameworkContentElement for target element. BindingExpression:Path=MyDayList; DataItem=null; target element is 'CollectionViewSource' (HashCode=58368655); target property is 'Source' (type 'Object')

I can't find a way to make a link between the dayList in the ListView ItemsSource, and the dayList in the CollectionRessource. Do you guys have an idea?

FYI: pre sorting the ObservableCollection is not doable, because of the nature of the Class i'm using.