Im getting this error when trying to create a node of my type "NewsItem"

Im using the latest umbraco 7.1.6

this is my config :

<uDateFoldersySettings>

    <DateFolders enabled="true">

        <!--- csv of doc type aliases which are the roots of where date folders should go (eg. news, blog)-->

        <RootDocTypeAliases>NewsOverview</RootDocTypeAliases>

        <!-- enables year folders -->

        <YearFolders enabled="true" docTypeAlias="uDateFoldersyFolderYear"/>

        <!-- enables month folders... note: this setting will not apply if year folders are disabled -->

        <MonthFolders enabled="true" docTypeAlias="uDateFoldersyFolderMonth"/>

        <!-- enables day folders... note: this setting will not apply if month folders are disabled -->

        <DayFolders enabled="false" docTypeAlias="uDateFoldersyFolderDay"/>

        <!-- csv of doc type aliases which will be put into folders -->

        <TargetDocTypeAliases>NewsItem</TargetDocTypeAliases>

        <!-- the date property - must be a date type -->

        <DatePropertyAlias>newsdate</DatePropertyAlias> (my date property is a date picker with time in my newsitem doctype)

        <FolderNameFormat>

            <!-- Valid values: M MM MMM MMMM == 3 03 Mar March -->

            <MonthFormat>MMMM</MonthFormat> 

            <!-- Valid formats: d dd == 9 09 -->

            <DayFormat>dd</DayFormat>

        </FolderNameFormat>

    </DateFolders>

</uDateFoldersySettings>

Am I doing something wrong with the date key?