diff --git a/src/main/java/serverutils/ServerUtilities.java b/src/main/java/serverutils/ServerUtilities.java
index c6d0a25c..faa4f184 100644
--- a/src/main/java/serverutils/ServerUtilities.java
+++ b/src/main/java/serverutils/ServerUtilities.java
@@ -65,7 +65,12 @@ public static CommandException errorFeatureDisabledServer(@Nullable ICommandSend
 
     @Mod.EventHandler
     public void onPreInit(FMLPreInitializationEvent event) {
+        // Keep string handling on US English, mainly to avoid the Turkish dotless I breaking case conversions.
+        // Number and date formatting stays on the player's locale, other mods read it to format their own output.
+        final Locale formatLocale = Locale.getDefault(Locale.Category.FORMAT);
         Locale.setDefault(Locale.US);
+        Locale.setDefault(Locale.Category.FORMAT, formatLocale);
+
         PROXY.preInit(event);
     }
 
diff --git a/src/main/java/serverutils/client/gui/GuiRestoreBackup.java b/src/main/java/serverutils/client/gui/GuiRestoreBackup.java
index ef929a02..9a823d47 100644
--- a/src/main/java/serverutils/client/gui/GuiRestoreBackup.java
+++ b/src/main/java/serverutils/client/gui/GuiRestoreBackup.java
@@ -18,6 +18,7 @@
 import java.util.Comparator;
 import java.util.LinkedHashMap;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
 import java.util.function.Consumer;
@@ -62,7 +63,8 @@
 @EventBusSubscriber(side = Side.CLIENT)
 public class GuiRestoreBackup extends GuiButtonListBase {
 
-    private static final DateFormat DATE_FORMAT = new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss");
+    // Root locale, BackupTask.BACKUP_NAME_PATTERN only matches ASCII digits.
+    private static final DateFormat DATE_FORMAT = new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss", Locale.ROOT);
     private static final Set<File> allBackupFiles = new ObjectOpenHashSet<>();
     private static Object2ObjectMap<String, List<File>> worldBackups;
     private final List<File> backupFiles;
diff --git a/src/main/java/serverutils/lib/util/StringUtils.java b/src/main/java/serverutils/lib/util/StringUtils.java
index fcb291cb..f85d2ed4 100644
--- a/src/main/java/serverutils/lib/util/StringUtils.java
+++ b/src/main/java/serverutils/lib/util/StringUtils.java
@@ -6,11 +6,13 @@
 import java.io.Reader;
 import java.math.RoundingMode;
 import java.text.DecimalFormat;
+import java.text.DecimalFormatSymbols;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Comparator;
 import java.util.HashMap;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.UUID;
 import java.util.regex.Pattern;
@@ -45,8 +47,13 @@ public class StringUtils {
             .compareToIgnoreCase(getID(o2, FLAG_ID_FIX));
 
     public static final Map<String, String> TEMP_MAP = new HashMap<>();
-    public static final DecimalFormat DOUBLE_FORMATTER_00 = new DecimalFormat("#0.00");
-    public static final DecimalFormat DOUBLE_FORMATTER_0 = new DecimalFormat("#0.0");
+    // Root locale, formatDouble0 and formatDouble00 trim the fraction by looking for a dot.
+    public static final DecimalFormat DOUBLE_FORMATTER_00 = new DecimalFormat(
+            "#0.00",
+            DecimalFormatSymbols.getInstance(Locale.ROOT));
+    public static final DecimalFormat DOUBLE_FORMATTER_0 = new DecimalFormat(
+            "#0.0",
+            DecimalFormatSymbols.getInstance(Locale.ROOT));
     public final static int[] INT_SIZE_TABLE = { 9, 99, 999, 9999, 99999, 999999, 9999999, 99999999, 999999999,
             Integer.MAX_VALUE };
 
diff --git a/src/main/java/serverutils/task/backup/ThreadBackup.java b/src/main/java/serverutils/task/backup/ThreadBackup.java
index 6cb5b191..98bfb09d 100644
--- a/src/main/java/serverutils/task/backup/ThreadBackup.java
+++ b/src/main/java/serverutils/task/backup/ThreadBackup.java
@@ -35,6 +35,7 @@
 import java.util.HashSet;
 import java.util.LinkedHashMap;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
 import java.util.zip.CRC32;
@@ -62,7 +63,8 @@
 
 public class ThreadBackup extends Thread {
 
-    private static final DateFormat DATE_FORMAT = new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss");
+    // Root locale, BackupTask.BACKUP_NAME_PATTERN only matches ASCII digits.
+    private static final DateFormat DATE_FORMAT = new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss", Locale.ROOT);
     private static long logMillis;
     private final File src0;
     private final String customName;