x:Bind in WinUI3 Binding to a datetime

I am trying to bind current DateTime to a textblock object in WinUI3.

xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:HabitTracker.Screens"
    xmlns:sys="using:System"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
    

... But my binding doesn't work. I get empty string on the UI while running the application.

I have the following namespace declaration:

xmlns:sys="using:System"

What am I missing?

Note: I also read this doc https://learn.microsoft.com/en-us/windows/uwp/data-binding/function-bindings although it is for UWP, not WinUi3 documentation.

I am using WindowsAppSDK 1.1.1