Add config in settings for forcing 24H time, determines default off CurrentCulture

osu.Game/Configuration/OsuConfigManager.cs

@@ -102,6 +102,8 @@ namespace osu.Game.Configuration
 
             SetDefault(OsuSetting.MenuParallax, true);
 
+            SetDefault(OsuSetting.Prefer24HourTime, false);
+
             // Gameplay
             SetDefault(OsuSetting.PositionalHitsounds, true); // replaced by level setting below, can be removed 20220703.
             SetDefault(OsuSetting.PositionalHitsoundsLevel, 0.2f, 0, 1);
@@ -287,6 +289,7 @@ namespace osu.Game.Configuration
         MenuVoice,
         CursorRotation,
         MenuParallax,
+        Prefer24HourTime,
         BeatmapDetailTab,
         BeatmapDetailModsFilter,
         Username,

osu.Game/Localisation/UserInterfaceStrings.cs

@@ -24,6 +24,11 @@ namespace osu.Game.Localisation
         /// </summary>
         public static LocalisableString CursorRotation => new TranslatableString(getKey(@"cursor_rotation"), @"Rotate cursor when dragging");
 
+        /// <summary>
+        /// "Prefer 24-hour time"
+        /// </summary>
+        public static LocalisableString Prefer24HourTime => new TranslatableString(getKey(@"prefer_24_hour_time"), @"Prefer 24-hour time");
+
         /// <summary>
         /// "Menu cursor size"
         /// </summary>

osu.Game/Overlays/Settings/Sections/UserInterface/GeneralSettings.cs

@@ -41,6 +41,11 @@ namespace osu.Game.Overlays.Settings.Sections.UserInterface
                     Current = config.GetBindable<double>(OsuSetting.UIHoldActivationDelay),
                     KeyboardStep = 50
                 },
+                new SettingsCheckbox
+                {
+                    LabelText = UserInterfaceStrings.Prefer24HourTime,
+                    Current = config.GetBindable<bool>(OsuSetting.Prefer24HourTime)
+                },
             };
         }
     }

osu.Game/Overlays/Toolbar/DigitalClockDisplay.cs

@@ -29,7 +29,21 @@ namespace osu.Game.Overlays.Toolbar
             }
         }
 
-        private bool format12H = true;
+        private bool format12H = false;
+
+        public bool Format12H
+        {
+            get => format12H;
+            set
+            {
+                if (format12H == value)
+                    return;
+
+                format12H = value;
+                updateMetrics();
+                UpdateDisplay(DateTimeOffset.Now); //Update realTime.Text immediately instead of waiting until next second
+            }
+        }
 
         [BackgroundDependencyLoader]
         private void load(OsuColour colours)
@@ -52,14 +66,14 @@ namespace osu.Game.Overlays.Toolbar
 
         protected override void UpdateDisplay(DateTimeOffset now)
         {
-            realTime.Text = format12H ? $"{now:hh:mm:ss tt}" : $"{now:HH:mm:ss}";
+            realTime.Text = format12H ? $"{now:h:mm:ss tt}" : $"{now:HH:mm:ss}";
             gameTime.Text = $"running {new TimeSpan(TimeSpan.TicksPerSecond * (int)(Clock.CurrentTime / 1000)):c}";
         }
 
         private void updateMetrics()
         {
             if (format12H)
-                Width = 74;
+                Width = 70;
             else
                 Width = showRuntime ? 66 : 45; // Allows for space for game time up to 99 days (in the padding area since this is quite rare).
 

osu.Game/Overlays/Toolbar/ToolbarClock.cs

@@ -1,6 +1,7 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System.Globalization;
 using osu.Framework.Allocation;
 using osu.Framework.Bindables;
 using osu.Framework.Extensions.Color4Extensions;
@@ -20,6 +21,7 @@ namespace osu.Game.Overlays.Toolbar
     public class ToolbarClock : OsuClickableContainer
     {
         private Bindable<ToolbarClockDisplayMode> clockDisplayMode;
+        private Bindable<bool> digitalPrefer24Hour;
 
         private Box hoverBackground;
         private Box flashBackground;
@@ -38,6 +40,7 @@ namespace osu.Game.Overlays.Toolbar
         private void load(OsuConfigManager config)
         {
             clockDisplayMode = config.GetBindable<ToolbarClockDisplayMode>(OsuSetting.ToolbarClockDisplayMode);
+            digitalPrefer24Hour = config.GetBindable<bool>(OsuSetting.Prefer24HourTime);
 
             Children = new Drawable[]
             {
@@ -94,6 +97,9 @@ namespace osu.Game.Overlays.Toolbar
 
                 analog.FadeTo(showAnalog ? 1 : 0);
             }, true);
+
+            digitalPrefer24Hour.BindValueChanged(prefer24H =>
+                digital.Format12H = prefer24H.NewValue ? false : CultureInfo.CurrentCulture.DateTimeFormat.ShortTimePattern.Contains("tt"), true);
         }
 
         protected override bool OnClick(ClickEvent e)