chore: Add missing DateTimeFormatter formats

src/SamplesApp/UITests.Shared/Windows_UI_Xaml_Controls/CalendarView/CalendarDatePicker_Features.xaml

@@ -29,6 +29,20 @@
 				<ComboBoxItem Content="{}{dayofweek.solo.abbreviated(2)}"></ComboBoxItem>
 				<ComboBoxItem Content="{}{dayofweek.solo.abbreviated(3)}"></ComboBoxItem>
 			</ComboBox>
+			<ComboBox x:Name="dateformat" Header="DateFormat">
+				<ComboBoxItem Content="{}{day.integer}/{month.integer}/{year.full}"></ComboBoxItem>
+				<ComboBoxItem Content="{}{month.full} {year.full}"></ComboBoxItem>
+				<ComboBoxItem Content="{}{month.full} {day.integer}"></ComboBoxItem>
+				<ComboBoxItem Content="{}{dayofweek.full}, {day.integer} {month.full} {year.full}"></ComboBoxItem>
+				<ComboBoxItem Content="{}{dayofweek.abbreviated}, {day.integer} {month.abbreviated} {year.full}"></ComboBoxItem>
+				<ComboBoxItem Content="{}{year.full}-{month.integer}-{day.integer}"></ComboBoxItem>
+				<ComboBoxItem Content="{}{day.integer}/{month.integer}/{year.abbreviated}"></ComboBoxItem>
+				<ComboBoxItem Content="{}{day.integer} {month.abbreviated} {year.full}"></ComboBoxItem>
+				<ComboBoxItem Content="{}{month.full} {day.integer}, {year.full}"></ComboBoxItem>
+				<ComboBoxItem Content="{}{month.abbreviated} {day.integer}, {year.full}"></ComboBoxItem>
+				<ComboBoxItem Content="{}{dayofweek.full}, {day.integer} {month.full} {year.full}"></ComboBoxItem>
+				<ComboBoxItem Content="{}{dayofweek.abbreviated}, {day.integer} {month.abbreviated} {year.abbreviated}"></ComboBoxItem>
+			</ComboBox>
 			<ComboBox x:Name="cid" Header="Calendar">
 				<ComboBoxItem>ChineseLunarCalendar</ComboBoxItem>
 				<ComboBoxItem IsSelected="True">GregorianCalendar</ComboBoxItem>
@@ -55,6 +69,7 @@
 				CalendarIdentifier="{Binding SelectedItem.Content, ElementName=cid, FallbackValue=GregorianCalendar}"
 				FirstDayOfWeek="{Binding SelectedItem.Content, ElementName=dow, FallbackValue=Sunday}"
 				DayOfWeekFormat="{Binding SelectedItem.Content, ElementName=dowf}"
+				DateFormat="{Binding SelectedItem.Content, ElementName=dateformat}"
 				IsTodayHighlighted="{Binding IsChecked, ElementName=today}"/>
 			<ToggleButton IsChecked="{Binding IsEnabled, ElementName=cdp1, Mode=TwoWay}">
 				IsEnabled

src/Uno.UI.RuntimeTests/Tests/Windows_Globalization/Given_DateTimeFormatter.cs

@@ -0,0 +1,134 @@
+using System;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Windows.Globalization.DateTimeFormatting;
+using System.Globalization;
+using Windows.Globalization;
+using System.Linq;
+using System.Collections.Generic;
+
+namespace Uno.UI.RuntimeTests.Tests.Windows_Globalization;
+
+[TestClass]
+public class Given_DateTimeFormatter
+{
+	[TestMethod]
+	public void When_CreatingWithFormatTemplate_ShouldInitializeCorrectly()
+	{
+		var formatter = new DateTimeFormatter("longdate");
+		Assert.IsNotNull(formatter);
+		Assert.AreEqual("longdate", formatter.Template);
+	}
+
+	[TestMethod]
+	public void When_UsingCustomLanguages_ShouldSetLanguagesCorrectly()
+	{
+		var languages = new[] { "fr-FR", "en-US" };
+		var formatter = new DateTimeFormatter("longdate", languages);
+
+		CollectionAssert.AreEqual(languages, formatter.Languages.ToList());
+	}
+
+	[TestMethod]
+	public void When_FormattingDateTimeOffset_ShouldProduceFormattedString()
+	{
+		var formatter = new DateTimeFormatter("longdate");
+		var dateToFormat = new DateTimeOffset(2024, 1, 15, 0, 0, 0, TimeSpan.Zero);
+
+		var formattedDate = formatter.Format(dateToFormat);
+		Assert.IsNotNull(formattedDate);
+		Assert.IsTrue(formattedDate.Length > 0);
+	}
+
+	[TestMethod]
+	public void When_SettingNumeralSystem_ShouldUpdateProperty()
+	{
+		var formatter = new DateTimeFormatter("longdate");
+		formatter.NumeralSystem = "arab";
+
+		Assert.AreEqual("arab", formatter.NumeralSystem);
+	}
+
+	[TestMethod]
+	public void When_CheckingPatterns_ShouldNotBeEmpty()
+	{
+		var formatter = new DateTimeFormatter("longdate");
+
+		Assert.IsTrue(formatter.Patterns.Count > 0);
+	}
+
+	[TestMethod]
+	public void When_CallingFormatWithTimeZone_ShouldThrowNotSupportedException()
+	{
+		var formatter = new DateTimeFormatter("longdate");
+		var dateToFormat = new DateTimeOffset(2024, 1, 15, 0, 0, 0, TimeSpan.Zero);
+
+		Assert.ThrowsException<NotSupportedException>(() =>
+			formatter.Format(dateToFormat, "UTC"));
+	}
+
+	[TestMethod]
+	public void When_CreatingFormatter_ShouldUseApplicationLanguages()
+	{
+		var formatter = new DateTimeFormatter("longdate");
+
+		CollectionAssert.AreEqual(ApplicationLanguages.Languages.ToList(), formatter.Languages.ToList());
+	}
+
+	[TestMethod]
+	public void When_FormattingDateVariants_ShouldProduceExpectedFormats()
+	{
+		var expectedResults = new Dictionary<string, string>
+		{
+			{ "{day.integer}/{month.integer}/{year.full}", "27/6/2024" },
+			{ "{month.full} {year.full}", "June 2024" },
+			{ "{month.full} {day.integer}", "June 27" },
+			{ "{dayofweek.abbreviated}, {day.integer} {month.abbreviated} {year.full}", "Thu, 27 Jun 2024" },
+			{ "{year.full}-{month.integer}-{day.integer}", "2024-6-27" },
+			{ "{day.integer}/{month.integer}/{year.abbreviated}", "27/6/24" },
+			{ "{day.integer} {month.abbreviated} {year.full}", "27 Jun 2024" },
+			{ "{month.full} {day.integer}, {year.full}", "June 27, 2024" },
+			{ "{month.abbreviated} {day.integer}, {year.full}", "Jun 27, 2024" },
+			{ "{dayofweek.full}, {day.integer} {month.full} {year.full}", "Thursday, 27 June 2024" },
+			{ "{dayofweek.abbreviated}, {day.integer} {month.abbreviated} {year.abbreviated}", "Thu, 27 Jun 24" }
+		};
+
+		foreach (var kvp in expectedResults)
+		{
+			var template = kvp.Key;
+			var expected = kvp.Value;
+
+			var formatter = new DateTimeFormatter(template);
+			var formattedDate = formatter.Format(new(2024, 6, 27, 14, 30, 0, TimeSpan.Zero));
+
+			Assert.AreEqual(expected, formattedDate, $"Mismatch for template: {template}");
+		}
+	}
+
+	// TODO(DT): Currently is throwing unexpected results on WinUI as well, can't compare the expected results
+	/* [TestMethod]
+	public void When_FormattingTimeVariants_ShouldProduceExpectedFormats()
+	{
+		var expectedResults = new Dictionary<string, string>
+		{
+			{ "{hour.integer}:{minute.integer}", "14:30" },
+			{ "{hour.integer}:{minute.integer}:{second.integer}", "14:30:00" },
+			{ "{hour.integer}:{minute.integer} {period.abbreviated(2)}", "2:30 PM" },
+			{ "{hour.integer}:{minute.integer}:{second.integer} {period.abbreviated(2)}", "2:30:00 PM" },
+			{ "{minute.integer}:{second.integer}", "30:00" },
+			{ "{second.integer}", "0" },
+			{ "{hour.integer}:{minute.integer}:{second.integer} UTC", "14:30:00 UTC" }
+		};
+
+		foreach (var kvp in expectedResults)
+		{
+			var template = kvp.Key;
+			var expected = kvp.Value;
+
+			var formatter = new DateTimeFormatter(template);
+			var formattedTime = formatter.Format(_testDate);
+
+			Assert.AreEqual(expected, formattedTime, $"Mismatch for template: {template}");
+			Console.WriteLine($"Template: {template}, Result: {formattedTime}");
+		}
+	}*/
+}

src/Uno.UWP/Globalization/DateTimeFormatting/DateTimeFormatter.cs

@@ -326,7 +326,9 @@ private IDictionary<string, string> BuildLookup(string language)
 			{ "timezone.abbreviated"                 , "zz" },
 			{ "timezone.full"                        , "zzz" },
 			{ "dayofweek"                            , "dddd" } ,
+			{ "day.integer"                          , "d" },
 			{ "day"                                  , "%d" } ,
+			{ "month.integer"                        , "M" },
 			{ "month"                                , "MMMM" } ,
 			{ "year"                                 , "yyyy" } ,
 			{ "hour.integer(1)"                      , "%h" },