diff --git a/CuckooChessEngine/src/chess/Game.java b/CuckooChessEngine/src/chess/Game.java
index b23a57f..b2d82d8 100644
--- a/CuckooChessEngine/src/chess/Game.java
+++ b/CuckooChessEngine/src/chess/Game.java
@@ -21,6 +21,7 @@ package chess;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.Locale;
 
 /**
  *
@@ -320,7 +321,7 @@ public class Game {
         for (int i = 0; i < moveList.size(); i++) {
             Move move = moveList.get(i);
             String strMove = TextIO.moveToString(pos, move, false);
-            moves.append(String.format(" %s", strMove));
+            moves.append(String.format(Locale.US, " %s", strMove));
             UndoInfo ui = new UndoInfo();
             pos.makeMove(move, ui);
         }
@@ -364,10 +365,10 @@ public class Game {
                     whiteMove = "...";
                 }
                 if (compressed) {
-                    ret.append(String.format("%d. %s %s ",
+                    ret.append(String.format(Locale.US, "%d. %s %s ",
                             pos.fullMoveCounter, whiteMove, blackMove));
                 } else {
-                    ret.append(String.format("%3d.  %-10s %-10s%n",
+                    ret.append(String.format(Locale.US, "%3d.  %-10s %-10s%n",
                             pos.fullMoveCounter, whiteMove, blackMove));
                 }
                 whiteMove = "";
@@ -381,10 +382,10 @@ public class Game {
                 whiteMove = "...";
             }
             if (compressed) {
-                ret.append(String.format("%d. %s %s ",
+                ret.append(String.format(Locale.US, "%d. %s %s ",
                         pos.fullMoveCounter, whiteMove, blackMove));
             } else {
-                ret.append(String.format("%3d.  %-8s %-8s%n",
+                ret.append(String.format(Locale.US, "%3d.  %-8s %-8s%n",
                         pos.fullMoveCounter, whiteMove, blackMove));
             }
         }
@@ -393,7 +394,7 @@ public class Game {
             if (compressed) {
                 ret.append(gameResult);
             } else {
-                ret.append(String.format("%s%n", gameResult));
+                ret.append(String.format(Locale.US, "%s%n", gameResult));
             }
         }
         return ret.toString();
diff --git a/CuckooChessEngine/src/chess/HumanPlayer.java b/CuckooChessEngine/src/chess/HumanPlayer.java
index e0e29f9..b443436 100644
--- a/CuckooChessEngine/src/chess/HumanPlayer.java
+++ b/CuckooChessEngine/src/chess/HumanPlayer.java
@@ -22,6 +22,7 @@ import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.util.List;
+import java.util.Locale;
 
 /**
  * A player that reads input from the keyboard.
@@ -39,7 +40,7 @@ public class HumanPlayer implements Player {
     public String getCommand(Position pos, boolean drawOffer, List<Position> history) {
         try {
             String color = pos.whiteMove ? "white" : "black";
-            System.out.print(String.format("Enter move (%s):", color));
+            System.out.print(String.format(Locale.US, "Enter move (%s):", color));
             String moveStr = in.readLine();
             if (moveStr == null)
                 return "quit";
diff --git a/CuckooChessEngine/src/chess/TextIO.java b/CuckooChessEngine/src/chess/TextIO.java
index 9283314..a13d904 100644
--- a/CuckooChessEngine/src/chess/TextIO.java
+++ b/CuckooChessEngine/src/chess/TextIO.java
@@ -18,6 +18,8 @@
 
 package chess;
 
+import java.util.Locale;
+
 /**
  *
  * @author petero
@@ -560,7 +562,7 @@ public class TextIO {
      */
     public static final String asciiBoard(Position pos) {
         StringBuilder ret = new StringBuilder(400);
-        String nl = String.format("%n");
+        String nl = String.format(Locale.US, "%n");
         ret.append("    +----+----+----+----+----+----+----+----+"); ret.append(nl);
         for (int y = 7; y >= 0; y--) {
             ret.append("    |");
diff --git a/CuckooChessEngine/src/guibase/ChessController.java b/CuckooChessEngine/src/guibase/ChessController.java
index 7e6b089..780afaa 100644
--- a/CuckooChessEngine/src/guibase/ChessController.java
+++ b/CuckooChessEngine/src/guibase/ChessController.java
@@ -36,6 +36,7 @@ import java.util.ArrayList;
 import java.util.Calendar;
 import java.util.GregorianCalendar;
 import java.util.List;
+import java.util.Locale;
 import java.util.Scanner;
 
 /**
@@ -71,20 +72,20 @@ public class ChessController {
 
         private void setSearchInfo() {
             StringBuilder buf = new StringBuilder();
-            buf.append(String.format("%n[%d] ", pvDepth));
+            buf.append(String.format(Locale.US, "%n[%d] ", pvDepth));
             if (pvUpperBound) {
                 buf.append("<=");
             } else if (pvLowerBound) {
                 buf.append(">=");
             }
             if (pvIsMate) {
-                buf.append(String.format("m%d", pvScore));
+                buf.append(String.format(Locale.US, "m%d", pvScore));
             } else {
-                buf.append(String.format("%.2f", pvScore / 100.0));
+                buf.append(String.format(Locale.US, "%.2f", pvScore / 100.0));
             }
             buf.append(pvStr);
-            buf.append(String.format("%n"));
-            buf.append(String.format("d:%d %d:%s t:%.2f n:%d nps:%d", currDepth,
+            buf.append(String.format(Locale.US, "%n"));
+            buf.append(String.format(Locale.US, "d:%d %d:%s t:%.2f n:%d nps:%d", currDepth,
                     currMoveNr, currMove, currTime / 1000.0, currNodes, currNps));
             final String newPV = buf.toString();
             gui.runOnUIThread(new Runnable() {
@@ -121,7 +122,7 @@ public class ChessController {
             Position pos = new Position(game.pos);
             UndoInfo ui = new UndoInfo();
             for (Move m : pv) {
-                buf.append(String.format(" %s", TextIO.moveToString(pos, m, false)));
+                buf.append(String.format(Locale.US, " %s", TextIO.moveToString(pos, m, false)));
                 pos.makeMove(m, ui);
             }
             pvStr = buf.toString();
@@ -211,17 +212,17 @@ public class ChessController {
             month = now.get(Calendar.MONTH) + 1;
             day = now.get(Calendar.DAY_OF_MONTH);
         }
-        pgn.append(String.format("[Date \"%04d.%02d.%02d\"]%n", year, month, day));
+        pgn.append(String.format(Locale.US, "[Date \"%04d.%02d.%02d\"]%n", year, month, day));
         String white = "Player";
         String black = ComputerPlayer.engineName;
         if (!humanIsWhite) {
             String tmp = white; white = black; black = tmp;
         }
-        pgn.append(String.format("[White \"%s\"]%n", white));
-        pgn.append(String.format("[Black \"%s\"]%n", black));
-        pgn.append(String.format("[Result \"%s\"]%n", game.getPGNResultString()));
+        pgn.append(String.format(Locale.US, "[White \"%s\"]%n", white));
+        pgn.append(String.format(Locale.US, "[Black \"%s\"]%n", black));
+        pgn.append(String.format(Locale.US, "[Result \"%s\"]%n", game.getPGNResultString()));
         if (!fen.equals(TextIO.startPosFEN)) {
-            pgn.append(String.format("[FEN \"%s\"]%n", fen));
+            pgn.append(String.format(Locale.US, "[FEN \"%s\"]%n", fen));
             pgn.append("[SetUp \"1\"]\n");
         }
         pgn.append("\n");
diff --git a/DroidFish/src/org/petero/droidfish/DroidFish.java b/DroidFish/src/org/petero/droidfish/DroidFish.java
index 4b4ee4f..b26f543 100644
--- a/DroidFish/src/org/petero/droidfish/DroidFish.java
+++ b/DroidFish/src/org/petero/droidfish/DroidFish.java
@@ -859,7 +859,7 @@ public class DroidFish extends Activity implements GUIInterface {
     }
 
     private final int getIntSetting(String settingName, int defaultValue) {
-        String tmp = settings.getString(settingName, String.format("%d", defaultValue));
+        String tmp = settings.getString(settingName, String.format(Locale.US, "%d", defaultValue));
         int value = Integer.parseInt(tmp);
         return value;
     }
@@ -1085,7 +1085,7 @@ public class DroidFish extends Activity implements GUIInterface {
                                      R.string.stockfish_engine);
             boolean analysis = (ctrl != null) && ctrl.analysisMode();
             if ((strength < 1000) && !analysis) {
-                engineTitleText.setText(String.format("%s: %d%%", eName, strength / 10));
+                engineTitleText.setText(String.format(Locale.US, "%s: %d%%", eName, strength / 10));
             } else {
                 engineTitleText.setText(eName);
             }
@@ -3107,7 +3107,7 @@ public class DroidFish extends Activity implements GUIInterface {
 
     @Override
     public void reportInvalidMove(Move m) {
-        String msg = String.format("%s %s-%s",
+        String msg = String.format(Locale.US, "%s %s-%s",
                 getString(R.string.invalid_move),
                 TextIO.squareToString(m.from), TextIO.squareToString(m.to));
         Toast.makeText(getApplicationContext(), msg, Toast.LENGTH_SHORT).show();
@@ -3115,14 +3115,14 @@ public class DroidFish extends Activity implements GUIInterface {
 
     @Override
     public void reportEngineName(String engine) {
-        String msg = String.format("%s: %s",
+        String msg = String.format(Locale.US, "%s: %s",
                 getString(R.string.engine), engine);
         Toast.makeText(getApplicationContext(), msg, Toast.LENGTH_SHORT).show();
     }
 
     @Override
     public void reportEngineError(String errMsg) {
-        String msg = String.format("%s: %s",
+        String msg = String.format(Locale.US, "%s: %s",
                 getString(R.string.engine_error), errMsg);
         Toast.makeText(getApplicationContext(), msg, Toast.LENGTH_LONG).show();
     }
diff --git a/DroidFish/src/org/petero/droidfish/activities/EditBoard.java b/DroidFish/src/org/petero/droidfish/activities/EditBoard.java
index 1c65a46..5797f2c 100644
--- a/DroidFish/src/org/petero/droidfish/activities/EditBoard.java
+++ b/DroidFish/src/org/petero/droidfish/activities/EditBoard.java
@@ -20,6 +20,7 @@ package org.petero.droidfish.activities;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Locale;
 
 import org.petero.droidfish.ChessBoard;
 import org.petero.droidfish.DroidFish;
@@ -549,8 +550,8 @@ public class EditBoard extends Activity {
             builder.setTitle(R.string.edit_move_counters);
             final EditText halfMoveClock = (EditText)content.findViewById(R.id.ed_cnt_halfmove);
             final EditText fullMoveCounter = (EditText)content.findViewById(R.id.ed_cnt_fullmove);
-            halfMoveClock.setText(String.format("%d", cb.pos.halfMoveClock));
-            fullMoveCounter.setText(String.format("%d", cb.pos.fullMoveCounter));
+            halfMoveClock.setText(String.format(Locale.US, "%d", cb.pos.halfMoveClock));
+            fullMoveCounter.setText(String.format(Locale.US, "%d", cb.pos.fullMoveCounter));
             final Runnable setCounters = new Runnable() {
                 public void run() {
                     try {
diff --git a/DroidFish/src/org/petero/droidfish/activities/EditPGN.java b/DroidFish/src/org/petero/droidfish/activities/EditPGN.java
index b161543..29c51fd 100644
--- a/DroidFish/src/org/petero/droidfish/activities/EditPGN.java
+++ b/DroidFish/src/org/petero/droidfish/activities/EditPGN.java
@@ -20,6 +20,7 @@ package org.petero.droidfish.activities;
 
 import java.io.File;
 import java.util.ArrayList;
+import java.util.Locale;
 
 import org.petero.droidfish.ColorTheme;
 import org.petero.droidfish.R;
@@ -382,7 +383,7 @@ public class EditPGN extends ListActivity {
             AlertDialog.Builder builder = new AlertDialog.Builder(this);
             builder.setTitle(R.string.delete_file_question);
             String name = new File(pgnFile.getName()).getName();
-            String msg = String.format(getString(R.string.delete_named_file), name);
+            String msg = String.format(Locale.US, getString(R.string.delete_named_file), name);
             builder.setMessage(msg);
             builder.setPositiveButton(R.string.yes, new DialogInterface.OnClickListener() {
                 public void onClick(DialogInterface dialog, int id) {
diff --git a/DroidFish/src/org/petero/droidfish/engine/DroidComputerPlayer.java b/DroidFish/src/org/petero/droidfish/engine/DroidComputerPlayer.java
index 0818352..514c906 100644
--- a/DroidFish/src/org/petero/droidfish/engine/DroidComputerPlayer.java
+++ b/DroidFish/src/org/petero/droidfish/engine/DroidComputerPlayer.java
@@ -555,13 +555,13 @@ public class DroidComputerPlayer {
             if (sr.wTime < 1) sr.wTime = 1;
             if (sr.bTime < 1) sr.bTime = 1;
             StringBuilder goStr = new StringBuilder(96);
-            goStr.append(String.format("go wtime %d btime %d", sr.wTime, sr.bTime));
+            goStr.append(String.format(Locale.US, "go wtime %d btime %d", sr.wTime, sr.bTime));
             if (sr.wInc > 0)
-                goStr.append(String.format(" winc %d", sr.wInc));
+                goStr.append(String.format(Locale.US, " winc %d", sr.wInc));
             if (sr.bInc > 0)
-                goStr.append(String.format(" binc %d", sr.bInc));
+                goStr.append(String.format(Locale.US, " binc %d", sr.bInc));
             if (sr.movesToGo > 0)
-                goStr.append(String.format(" movestogo %d", sr.movesToGo));
+                goStr.append(String.format(Locale.US, " movestogo %d", sr.movesToGo));
             if (sr.ponderMove != null)
                 goStr.append(" ponder");
             if (sr.searchMoves != null) {
diff --git a/DroidFish/src/org/petero/droidfish/engine/LocalPipe.java b/DroidFish/src/org/petero/droidfish/engine/LocalPipe.java
index 82477b8..799800c 100644
--- a/DroidFish/src/org/petero/droidfish/engine/LocalPipe.java
+++ b/DroidFish/src/org/petero/droidfish/engine/LocalPipe.java
@@ -1,6 +1,7 @@
 package org.petero.droidfish.engine;
 
 import java.util.LinkedList;
+import java.util.Locale;
 
 /** Implements line-based text communication between threads. */
 public class LocalPipe {
@@ -9,13 +10,13 @@ public class LocalPipe {
 
     /** Write a line to the pipe. */
     public final synchronized void printLine(String format) {
-        String s = String.format(format, new Object[]{});
+        String s = String.format(Locale.US, format, new Object[]{});
         addLine(s);
     }
 
     /** Write a line to the pipe. */
     public final synchronized void printLine(String format, Object ... args) {
-        String s = String.format(format, args);
+        String s = String.format(Locale.US, format, args);
         addLine(s);
     }
 
diff --git a/DroidFish/src/org/petero/droidfish/engine/UCIEngineBase.java b/DroidFish/src/org/petero/droidfish/engine/UCIEngineBase.java
index 8e15923..15f4253 100644
--- a/DroidFish/src/org/petero/droidfish/engine/UCIEngineBase.java
+++ b/DroidFish/src/org/petero/droidfish/engine/UCIEngineBase.java
@@ -111,7 +111,7 @@ public abstract class UCIEngineBase implements UCIEngine {
 
     @Override
     public void setOption(String name, int value) {
-        setOption(name, String.format("%d", value));
+        setOption(name, String.format(Locale.US, "%d", value));
     }
 
     @Override
@@ -127,7 +127,7 @@ public abstract class UCIEngineBase implements UCIEngine {
         String currVal = currOptions.get(lcName);
         if (value.equals(currVal))
             return;
-        writeLineToEngine(String.format("setoption name %s value %s", name, value));
+        writeLineToEngine(String.format(Locale.US, "setoption name %s value %s", name, value));
         currOptions.put(lcName, value);
     }
 }
diff --git a/DroidFish/src/org/petero/droidfish/gamelogic/DroidChessController.java b/DroidFish/src/org/petero/droidfish/gamelogic/DroidChessController.java
index fd343fd..69948e8 100644
--- a/DroidFish/src/org/petero/droidfish/gamelogic/DroidChessController.java
+++ b/DroidFish/src/org/petero/droidfish/gamelogic/DroidChessController.java
@@ -628,7 +628,7 @@ public class DroidChessController {
                     continue;
                 if (i > 0)
                     buf.append('\n');
-                buf.append(String.format("[%d] ", pvi.depth));
+                buf.append(String.format(Locale.US, "[%d] ", pvi.depth));
                 boolean negateScore = !whiteMove && gui.whiteBasedScores();
                 if (pvi.upperBound || pvi.lowerBound) {
                     boolean upper = pvi.upperBound ^ negateScore;
@@ -636,9 +636,9 @@ public class DroidChessController {
                 }
                 int score = negateScore ? -pvi.score : pvi.score;
                 if (pvi.isMate) {
-                    buf.append(String.format("m%d", score));
+                    buf.append(String.format(Locale.US, "m%d", score));
                 } else {
-                    buf.append(String.format("%.2f", score / 100.0));
+                    buf.append(String.format(Locale.US, "%.2f", score / 100.0));
                 }
 
                 buf.append(pvi.pvStr);
@@ -715,7 +715,7 @@ public class DroidChessController {
                 UndoInfo ui = new UndoInfo();
                 if (ponderMove != null) {
                     String moveStr = TextIO.moveToString(tmpPos, ponderMove, false, localPt());
-                    buf.append(String.format(" [%s]", moveStr));
+                    buf.append(String.format(Locale.US, " [%s]", moveStr));
                     tmpPos.makeMove(ponderMove, ui);
                 }
                 for (Move m : pv.pv) {
@@ -724,7 +724,7 @@ public class DroidChessController {
                     if (!TextIO.isValid(tmpPos, m))
                         break;
                     String moveStr = TextIO.moveToString(tmpPos, m, false, localPt());
-                    buf.append(String.format(" %s", moveStr));
+                    buf.append(String.format(Locale.US, " %s", moveStr));
                     tmpPos.makeMove(m, ui);
                 }
                 pv.pvStr = buf.toString();
@@ -897,7 +897,7 @@ public class DroidChessController {
             if (computerPlayer != null) {
                 engine = computerPlayer.getEngineName();
                 if (strength < 1000)
-                    engine += String.format(" (%.1f%%)", strength * 0.1);
+                    engine += String.format(Locale.US, " (%.1f%%)", strength * 0.1);
             }
             String player = gui.playerName();
             String white = gameMode.playerWhite() ? player : engine;
@@ -909,7 +909,7 @@ public class DroidChessController {
     private final synchronized void updatePlayerNames(String engineName) {
         if (game != null) {
             if (strength < 1000)
-                engineName += String.format(" (%.1f%%)", strength * 0.1);
+                engineName += String.format(Locale.US, " (%.1f%%)", strength * 0.1);
             String white = gameMode.playerWhite() ? game.tree.white : engineName;
             String black = gameMode.playerBlack() ? game.tree.black : engineName;
             game.tree.setPlayerNames(white, black);
diff --git a/DroidFish/src/org/petero/droidfish/gamelogic/GameTree.java b/DroidFish/src/org/petero/droidfish/gamelogic/GameTree.java
index cd885ed..19d9186 100644
--- a/DroidFish/src/org/petero/droidfish/gamelogic/GameTree.java
+++ b/DroidFish/src/org/petero/droidfish/gamelogic/GameTree.java
@@ -83,7 +83,7 @@ public class GameTree {
             int year = now.get(Calendar.YEAR);
             int month = now.get(Calendar.MONTH) + 1;
             int day = now.get(Calendar.DAY_OF_MONTH);
-            date = String.format("%04d.%02d.%02d", year, month, day);
+            date = String.format(Locale.US, "%04d.%02d.%02d", year, month, day);
         }
         round = "?";
         white = "?";
diff --git a/DroidFish/src/org/petero/droidfish/gamelogic/TextIO.java b/DroidFish/src/org/petero/droidfish/gamelogic/TextIO.java
index c6c2338..27358d5 100644
--- a/DroidFish/src/org/petero/droidfish/gamelogic/TextIO.java
+++ b/DroidFish/src/org/petero/droidfish/gamelogic/TextIO.java
@@ -20,6 +20,7 @@ package org.petero.droidfish.gamelogic;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Locale;
 
 import org.petero.droidfish.PGNOptions;
 import org.petero.droidfish.R;
@@ -703,7 +704,7 @@ public class TextIO {
      */
     public static final String asciiBoard(Position pos) {
         StringBuilder ret = new StringBuilder(400);
-        String nl = String.format("%n");
+        String nl = String.format(Locale.US, "%n");
         ret.append("    +----+----+----+----+----+----+----+----+"); ret.append(nl);
         for (int y = 7; y >= 0; y--) {
             ret.append("    |");