diff --git a/AquaMai.Mods/Fix/FixLocaleIssues.cs b/AquaMai.Mods/Fix/FixLocaleIssues.cs
new file mode 100644
index 00000000..b02c4ac1
--- /dev/null
+++ b/AquaMai.Mods/Fix/FixLocaleIssues.cs
@@ -0,0 +1,79 @@
+using System;
+using System.Globalization;
+using System.Threading;
+using AquaMai.Config.Attributes;
+using HarmonyLib;
+using JetBrains.Annotations;
+using Manager;
+using MelonLoader;
+
+namespace AquaMai.Mods.Fix;
+
+// Fixes various locale issues that pop up if the game runs in a different locale than ja-JP.
+[ConfigSection(exampleHidden: true, defaultOn: true)]
+public class FixLocaleIssues
+{
+    private static readonly CultureInfo JapanCultureInfo = new("ja-JP");
+    [CanBeNull] private static TimeZoneInfo _tokyoStandardTime;
+
+    public static void OnBeforePatch()
+    {
+        try
+        {
+            _tokyoStandardTime = TimeZoneInfo.FindSystemTimeZoneById("Tokyo Standard Time");
+        }
+        catch (Exception e) when (e is TimeZoneNotFoundException or InvalidTimeZoneException)
+        {
+            _tokyoStandardTime = TimeZoneInfo.CreateCustomTimeZone(
+                "Tokyo Standard Time",
+                TimeManager.JpTime,
+                "(UTC+09:00) Osaka, Sapporo, Tokyo",
+                "Tokyo Standard Time",
+                "Tokyo Daylight Time",
+                null,
+                true);
+        }
+        catch (Exception e)
+        {
+            MelonLogger.Warning($"Could not get JST timezone, DateTime.Now patch will not work: {e.StackTrace}");
+        }
+    }
+
+    // This covers all calls to T.Parse(String) or T.Parse(String, NumberStyles)
+    // where T is a number. Sets the current thread's culture to Japan before calling
+    // the original getter, since that's what the original getter depends on.
+    //
+    // While we already set the thread's culture on the OnBeforePatch lifecycle hook,
+    // it seems to not apply to the game at all for some reason.
+    [HarmonyPrefix]
+    [HarmonyPatch(typeof(NumberFormatInfo), "get_CurrentInfo")]
+    public static bool NumberFormatInfo_get_CurrentInfo(ref NumberFormatInfo __result)
+    {
+        __result = JapanCultureInfo.NumberFormat;
+        return false;
+    }
+
+    // Same for datetimes.
+    [HarmonyPrefix]
+    [HarmonyPatch(typeof(DateTimeFormatInfo), "get_CurrentInfo")]
+    public static bool DateTimeFormatInfo_get_CurrentInfo(ref DateTimeFormatInfo __result)
+    {
+        __result = JapanCultureInfo.DateTimeFormat;
+        return false;
+    }
+    
+    // Forces local timezone to be UTC+9, since segatools didn't patch it properly until recent versions,
+    // which doesn't actually work well with maimai.
+    [HarmonyPrefix]
+    [HarmonyPatch(typeof(DateTime), "get_Now")]
+    private static bool DateTime_get_Now(ref DateTime __result)
+    {
+        if (_tokyoStandardTime == null)
+        {
+            return true;
+        }
+
+        __result = TimeZoneInfo.ConvertTimeFromUtc(DateTime.UtcNow, _tokyoStandardTime!);
+        return false;
+    }
+}