diff --git a/DesktopClock.Tests/DateTimeTests.cs b/DesktopClock.Tests/DateTimeTests.cs
index 16862d7..bb5cc87 100644
--- a/DesktopClock.Tests/DateTimeTests.cs
+++ b/DesktopClock.Tests/DateTimeTests.cs
@@ -4,39 +4,6 @@ namespace DesktopClock.Tests;
 
 public class DateTimeTests
 {
-    [Fact]
-    public void TimeZones_ShouldContainSystemTimeZones()
-    {
-        // Act
-        var timeZones = DateTimeUtil.TimeZones;
-
-        // Assert
-        Assert.NotEmpty(timeZones);
-        Assert.Contains(timeZones, tz => tz.Id == "UTC");
-    }
-
-    [Theory]
-    [InlineData("UTC", true)]
-    [InlineData("Pacific Standard Time", true)]
-    [InlineData("NonExistentTimeZone", false)]
-    public void TryFindSystemTimeZoneById_ShouldReturnExpectedResult(string timeZoneId, bool expectedResult)
-    {
-        // Act
-        var result = DateTimeUtil.TryFindSystemTimeZoneById(timeZoneId, out var timeZoneInfo);
-
-        // Assert
-        Assert.Equal(expectedResult, result);
-        if (expectedResult)
-        {
-            Assert.NotNull(timeZoneInfo);
-            Assert.Equal(timeZoneId, timeZoneInfo.Id);
-        }
-        else
-        {
-            Assert.Null(timeZoneInfo);
-        }
-    }
-
     [Theory]
     [InlineData("2024-07-15T00:00:00Z", "00:00:00")]
     [InlineData("2024-07-15T00:00:00Z", "01:00:00")]
diff --git a/DesktopClock/DateFormatExample.cs b/DesktopClock/DateFormatExample.cs
index 45ec038..d6b9416 100644
--- a/DesktopClock/DateFormatExample.cs
+++ b/DesktopClock/DateFormatExample.cs
@@ -2,9 +2,6 @@
 using System.Collections.Generic;
 using System.Globalization;
 using System.Linq;
-using System.Windows.Data;
-using System.Windows.Markup;
-using DesktopClock.Properties;
 
 namespace DesktopClock;
 
diff --git a/DesktopClock/DateTimeUtil.cs b/DesktopClock/DateTimeUtil.cs
index 49724b0..38d45a0 100644
--- a/DesktopClock/DateTimeUtil.cs
+++ b/DesktopClock/DateTimeUtil.cs
@@ -1,29 +1,9 @@
 using System;
-using System.Collections.Generic;
 
 namespace DesktopClock;
 
 public static class DateTimeUtil
 {
-    /// <summary>
-    /// A cached collection of all the time zones about which information is available on the local system.
-    /// </summary>
-    public static IReadOnlyCollection<TimeZoneInfo> TimeZones { get; } = TimeZoneInfo.GetSystemTimeZones();
-
-    public static bool TryFindSystemTimeZoneById(string timeZoneId, out TimeZoneInfo timeZoneInfo)
-    {
-        try
-        {
-            timeZoneInfo = TimeZoneInfo.FindSystemTimeZoneById(timeZoneId);
-            return true;
-        }
-        catch (TimeZoneNotFoundException)
-        {
-            timeZoneInfo = null;
-            return false;
-        }
-    }
-
     /// <summary>
     /// Converts a DateTime to a DateTimeOffset, without risking any onerous exceptions
     /// the framework quite unfortunately throws within the DateTimeOffset constructor,
@@ -45,4 +25,4 @@ public static DateTimeOffset ToDateTimeOffset(this DateTime dt, TimeSpan offset)
 
         return new DateTimeOffset(dt.Ticks, offset);
     }
-}
\ No newline at end of file
+}
diff --git a/DesktopClock/Properties/Settings.cs b/DesktopClock/Properties/Settings.cs
index 8ae0248..0b4f5e4 100644
--- a/DesktopClock/Properties/Settings.cs
+++ b/DesktopClock/Properties/Settings.cs
@@ -328,8 +328,18 @@ public void ScaleHeight(double steps)
     /// <summary>
     /// Gets the time zone selected in settings, or local by default.
     /// </summary>
-    public TimeZoneInfo GetTimeZoneInfo() =>
-        DateTimeUtil.TryFindSystemTimeZoneById(TimeZone, out var timeZoneInfo) ? timeZoneInfo : TimeZoneInfo.Local;
+    public TimeZoneInfo GetTimeZoneInfo()
+    {
+
+        try
+        {
+            return TimeZoneInfo.FindSystemTimeZoneById(TimeZone);
+        }
+        catch (TimeZoneNotFoundException)
+        {
+            return TimeZoneInfo.Local;
+        }
+    }
 
     public void Dispose()
     {
diff --git a/DesktopClock/SettingsWindow.xaml b/DesktopClock/SettingsWindow.xaml
index afb662a..5eae2e6 100644
--- a/DesktopClock/SettingsWindow.xaml
+++ b/DesktopClock/SettingsWindow.xaml
@@ -26,7 +26,7 @@
                     <ComboBox Grid.Column="1"
                               DisplayMemberPath="Example"
                               ItemsSource="{x:Static local:DateFormatExample.DefaultExamples}"
-                              SelectionChanged="FormatComboBox_SelectionChanged" />
+                              SelectionChanged="SelectFormat" />
                 </Grid>
                 <TextBlock Text=".NET format string for the time shown on the clock. Format specific parts inside { and }."
                            FontStyle="Italic"
diff --git a/DesktopClock/SettingsWindow.xaml.cs b/DesktopClock/SettingsWindow.xaml.cs
index ed3280e..5934613 100644
--- a/DesktopClock/SettingsWindow.xaml.cs
+++ b/DesktopClock/SettingsWindow.xaml.cs
@@ -1,7 +1,6 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Runtime.Serialization;
 using System.Windows;
 using System.Windows.Controls;
 using System.Windows.Media;
@@ -20,14 +19,18 @@ public SettingsWindow()
         DataContext = new SettingsWindowViewModel(Settings.Default);
     }
 
-    private void FormatComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
+    private SettingsWindowViewModel ViewModel => (SettingsWindowViewModel)DataContext;
+
+    private void SelectFormat(object sender, SelectionChangedEventArgs e)
     {
-        var formatExample = e.AddedItems[0] as DateFormatExample;
+        var value = e.AddedItems[0] as DateFormatExample;
 
-        if (formatExample == null)
+        if (value == null)
+        {
             return;
+        }
 
-        ((SettingsWindowViewModel)DataContext).Settings.Format = formatExample.Format;
+        ViewModel.Settings.Format = value.Format;
     }
 
     private void BrowseBackgroundImagePath(object sender, RoutedEventArgs e)
@@ -42,7 +45,7 @@ private void BrowseBackgroundImagePath(object sender, RoutedEventArgs e)
             return;
         }
 
-        ((SettingsWindowViewModel)DataContext).Settings.BackgroundImagePath = openFileDialog.FileName;
+        ViewModel.Settings.BackgroundImagePath = openFileDialog.FileName;
     }
 
     private void BrowseWavFilePath(object sender, RoutedEventArgs e)
@@ -57,7 +60,7 @@ private void BrowseWavFilePath(object sender, RoutedEventArgs e)
             return;
         }
 
-        ((SettingsWindowViewModel)DataContext).Settings.WavFilePath = openFileDialog.FileName;
+        ViewModel.Settings.WavFilePath = openFileDialog.FileName;
     }
 }
 
@@ -72,14 +75,24 @@ public SettingsWindowViewModel(Settings settings)
         TimeZones = TimeZoneInfo.GetSystemTimeZones().Select(tz => tz.Id).ToList();
     }
 
+    /// <summary>
+    /// All available font families reported by the system.
+    /// </summary>
     public IList<string> FontFamilies { get; }
+
+    /// <summary>
+    /// All available time zones reported by the system.
+    /// </summary>
     public IList<string> TimeZones { get; }
 
     /// <summary>
-    /// Sets the format string in settings to the given string.
+    /// Sets the format string in settings.
     /// </summary>
     [RelayCommand]
-    public void SetFormat(DateFormatExample formatExample) => Settings.Default.Format = formatExample.Format;
+    public void SetFormat(DateFormatExample value)
+    {
+        Settings.Default.Format = value.Format;
+    }
 
     /// <summary>
     /// Disables countdown mode by resetting the value to default.