diff --git a/packages/SystemUI/plugin/src/com/android/systemui/plugins/ClockPlugin.java b/packages/SystemUI/plugin/src/com/android/systemui/plugins/ClockPlugin.java
index 6c6c9270bc84a..3058d94661210 100644
--- a/packages/SystemUI/plugin/src/com/android/systemui/plugins/ClockPlugin.java
+++ b/packages/SystemUI/plugin/src/com/android/systemui/plugins/ClockPlugin.java
@@ -126,6 +126,13 @@ public interface ClockPlugin extends Plugin {
      */
     default void onTimeZoneChanged(TimeZone timeZone) {}
 
+    /**
+     * Notifies that the time format has changed.
+     *
+     * @param timeFormat "12" for 12-hour format, "24" for 24-hour format
+     */
+    default void onTimeFormatChanged(String timeFormat) {}
+
     /**
      * Indicates whether the keyguard status area (date) should be shown below
      * the clock.
diff --git a/packages/SystemUI/res-keyguard/layout/keyguard_clock_switch.xml b/packages/SystemUI/res-keyguard/layout/keyguard_clock_switch.xml
index c82bda6620bd7..19f82480284e0 100644
--- a/packages/SystemUI/res-keyguard/layout/keyguard_clock_switch.xml
+++ b/packages/SystemUI/res-keyguard/layout/keyguard_clock_switch.xml
@@ -73,13 +73,15 @@
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:gravity="right"
-            android:textSize="80dp"
+            android:textSize="100dp"
             android:letterSpacing="0.02"
             android:lineSpacingMultiplier=".8"
             android:includeFontPadding="false"
             android:fontFamily="@font/clock"
             android:typeface="monospace"
             android:elegantTextHeight="false"
+            dozeWeight="200"
+            lockScreenWeight="300"
         />
     </FrameLayout>
     <FrameLayout
@@ -95,13 +97,15 @@
             android:layout_height="wrap_content"
             android:layout_gravity="center_horizontal"
             android:gravity="center_horizontal"
-            android:textSize="180dp"
+            android:textSize="200dp"
             android:letterSpacing="0.02"
             android:lineSpacingMultiplier=".8"
             android:includeFontPadding="false"
             android:fontFamily="@font/clock"
             android:typeface="monospace"
             android:elegantTextHeight="false"
+            dozeWeight="100"
+            lockScreenWeight="400"
         />
     </FrameLayout>
     <include layout="@layout/keyguard_status_area"
diff --git a/packages/SystemUI/res-keyguard/values/attrs.xml b/packages/SystemUI/res-keyguard/values/attrs.xml
index 293b683497f83..bfcc56cdc660d 100644
--- a/packages/SystemUI/res-keyguard/values/attrs.xml
+++ b/packages/SystemUI/res-keyguard/values/attrs.xml
@@ -39,4 +39,9 @@
     </declare-styleable>
 
     <attr name="passwordStyle" format="reference" />
+
+    <declare-styleable name="AnimatableClockView">
+        <attr name="dozeWeight" format="integer" />
+        <attr name="lockScreenWeight" format="integer" />
+    </declare-styleable>
 </resources>
diff --git a/packages/SystemUI/res-keyguard/values/styles.xml b/packages/SystemUI/res-keyguard/values/styles.xml
index bc48e8fe3eea2..71a1cc292ec90 100644
--- a/packages/SystemUI/res-keyguard/values/styles.xml
+++ b/packages/SystemUI/res-keyguard/values/styles.xml
@@ -137,5 +137,4 @@
         <item name="android:shadowColor">@color/keyguard_shadow_color</item>
         <item name="android:shadowRadius">?attr/shadowRadius</item>
     </style>
-
 </resources>
diff --git a/packages/SystemUI/src/com/android/keyguard/AnimatableClockController.java b/packages/SystemUI/src/com/android/keyguard/AnimatableClockController.java
index 3157a5a8fc5b5..7c6a27446c786 100644
--- a/packages/SystemUI/src/com/android/keyguard/AnimatableClockController.java
+++ b/packages/SystemUI/src/com/android/keyguard/AnimatableClockController.java
@@ -24,6 +24,8 @@ import com.android.settingslib.Utils;
 import com.android.systemui.plugins.statusbar.StatusBarStateController;
 import com.android.systemui.util.ViewController;
 
+import java.util.TimeZone;
+
 /**
  * Controls the color of a GradientTextClock.
  */
@@ -62,12 +64,26 @@ public class AnimatableClockController extends ViewController<AnimatableClockVie
     }
 
     /**
-     * Updates the time for this view.
+     * Updates the time for the view.
      */
     public void refreshTime() {
         mView.refreshTime();
     }
 
+    /**
+     * Updates the timezone for the view.
+     */
+    public void onTimeZoneChanged(TimeZone timeZone) {
+        mView.onTimeZoneChanged(timeZone);
+    }
+
+    /**
+     * Trigger a time format update
+     */
+    public void refreshFormat() {
+        mView.refreshFormat();
+    }
+
     private void initColors() {
         mLockScreenColors[0] = Utils.getColorAttrDefaultColor(getContext(),
                 com.android.systemui.R.attr.wallpaperTextColor);
diff --git a/packages/SystemUI/src/com/android/keyguard/AnimatableClockView.java b/packages/SystemUI/src/com/android/keyguard/AnimatableClockView.java
index 6d1d42e2988ba..ca99563986b42 100644
--- a/packages/SystemUI/src/com/android/keyguard/AnimatableClockView.java
+++ b/packages/SystemUI/src/com/android/keyguard/AnimatableClockView.java
@@ -19,13 +19,17 @@ package com.android.keyguard;
 import android.annotation.FloatRange;
 import android.annotation.IntRange;
 import android.content.Context;
+import android.content.res.TypedArray;
 import android.graphics.Canvas;
 import android.icu.text.DateTimePatternGenerator;
 import android.text.format.DateFormat;
 import android.util.AttributeSet;
 import android.widget.TextView;
 
+import com.android.systemui.R;
+
 import java.util.Calendar;
+import java.util.TimeZone;
 
 import kotlin.Unit;
 
@@ -38,11 +42,14 @@ public class AnimatableClockView extends TextView {
     private static final CharSequence FORMAT_24_HOUR = "HH\nmm";
     private static final long ANIM_DURATION = 300;
 
+    private final Calendar mTime = Calendar.getInstance();
+
     private CharSequence mFormat;
     private CharSequence mDescFormat;
-    private Calendar mTime = Calendar.getInstance();
     private int[] mDozingColors;
     private int[] mLockScreenColors;
+    private final int mDozingWeight;
+    private final int mLockScreenWeight;
 
     private TextAnimator mTextAnimator = null;
     private Runnable mOnTextAnimatorInitialized;
@@ -62,13 +69,21 @@ public class AnimatableClockView extends TextView {
     public AnimatableClockView(Context context, AttributeSet attrs, int defStyleAttr,
             int defStyleRes) {
         super(context, attrs, defStyleAttr, defStyleRes);
-        updateTimeFormat();
+        TypedArray ta = context.obtainStyledAttributes(
+                attrs, R.styleable.AnimatableClockView, defStyleAttr, defStyleRes);
+        try {
+            mDozingWeight = ta.getInt(R.styleable.AnimatableClockView_dozeWeight, 100);
+            mLockScreenWeight = ta.getInt(R.styleable.AnimatableClockView_lockScreenWeight, 300);
+        } finally {
+            ta.recycle();
+        }
+        refreshFormat();
     }
 
     @Override
     public void onAttachedToWindow() {
         super.onAttachedToWindow();
-        updateTimeFormat();
+        refreshFormat();
     }
 
     @Override
@@ -82,6 +97,11 @@ public class AnimatableClockView extends TextView {
         setContentDescription(DateFormat.format(mDescFormat, mTime));
     }
 
+    void onTimeZoneChanged(TimeZone timeZone) {
+        mTime.setTimeZone(timeZone);
+        refreshFormat();
+    }
+
     @Override
     protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
         super.onMeasure(widthMeasureSpec, heightMeasureSpec);
@@ -113,7 +133,7 @@ public class AnimatableClockView extends TextView {
     }
 
     void animateDoze(boolean isDozing, boolean animate) {
-        setTextStyle(isDozing ? 100 : 300 /* weight */,
+        setTextStyle(isDozing ? mDozingWeight : mLockScreenWeight /* weight */,
                 -1,
                 isDozing ? mDozingColors : mLockScreenColors,
                 animate);
@@ -144,10 +164,11 @@ public class AnimatableClockView extends TextView {
         }
     }
 
-    private void updateTimeFormat() {
+    void refreshFormat() {
         final boolean use24HourFormat = DateFormat.is24HourFormat(getContext());
         mFormat =  use24HourFormat ? FORMAT_24_HOUR : FORMAT_12_HOUR;
         mDescFormat = getBestDateTimePattern(getContext(), use24HourFormat ? "Hm" : "hm");
+        refreshTime();
     }
 
     private static String getBestDateTimePattern(Context context, String skeleton) {
diff --git a/packages/SystemUI/src/com/android/keyguard/KeyguardClockSwitch.java b/packages/SystemUI/src/com/android/keyguard/KeyguardClockSwitch.java
index 68405a1fca687..0a78efa8ea035 100644
--- a/packages/SystemUI/src/com/android/keyguard/KeyguardClockSwitch.java
+++ b/packages/SystemUI/src/com/android/keyguard/KeyguardClockSwitch.java
@@ -401,6 +401,17 @@ public class KeyguardClockSwitch extends RelativeLayout {
         }
     }
 
+    /**
+     * Notifies that the time format has changed.
+     *
+     * @param timeFormat "12" for 12-hour format, "24" for 24-hour format
+     */
+    public void onTimeFormatChanged(String timeFormat) {
+        if (mClockPlugin != null) {
+            mClockPlugin.onTimeFormatChanged(timeFormat);
+        }
+    }
+
     void updateColors(ColorExtractor.GradientColors colors) {
         mSupportsDarkText = colors.supportsDarkText();
         mColorPalette = colors.getColorPalette();
diff --git a/packages/SystemUI/src/com/android/keyguard/KeyguardClockSwitchController.java b/packages/SystemUI/src/com/android/keyguard/KeyguardClockSwitchController.java
index 829ff9771fb41..4d6e8a90e57b1 100644
--- a/packages/SystemUI/src/com/android/keyguard/KeyguardClockSwitchController.java
+++ b/packages/SystemUI/src/com/android/keyguard/KeyguardClockSwitchController.java
@@ -17,7 +17,9 @@
 package com.android.keyguard;
 
 import android.app.WallpaperManager;
+import android.content.ContentResolver;
 import android.content.res.Resources;
+import android.provider.Settings;
 import android.text.format.DateFormat;
 import android.util.TypedValue;
 import android.view.View;
@@ -90,6 +92,7 @@ public class KeyguardClockSwitchController extends ViewController<KeyguardClockS
     };
 
     private ClockManager.ClockChangedListener mClockChangedListener = this::setClockPlugin;
+    private String mTimeFormat;
 
     @Inject
     public KeyguardClockSwitchController(
@@ -98,7 +101,8 @@ public class KeyguardClockSwitchController extends ViewController<KeyguardClockS
             StatusBarStateController statusBarStateController,
             SysuiColorExtractor colorExtractor, ClockManager clockManager,
             KeyguardSliceViewController keyguardSliceViewController,
-            NotificationIconAreaController notificationIconAreaController) {
+            NotificationIconAreaController notificationIconAreaController,
+            ContentResolver contentResolver) {
         super(keyguardClockSwitch);
         mResources = resources;
         mStatusBarStateController = statusBarStateController;
@@ -106,6 +110,7 @@ public class KeyguardClockSwitchController extends ViewController<KeyguardClockS
         mClockManager = clockManager;
         mKeyguardSliceViewController = keyguardSliceViewController;
         mNotificationIconAreaController = notificationIconAreaController;
+        mTimeFormat = Settings.System.getString(contentResolver, Settings.System.TIME_12_24);
     }
 
     /**
@@ -246,12 +251,26 @@ public class KeyguardClockSwitchController extends ViewController<KeyguardClockS
 
     void updateTimeZone(TimeZone timeZone) {
         mView.onTimeZoneChanged(timeZone);
+        if (mNewLockScreenClockViewController != null) {
+            mNewLockScreenClockViewController.onTimeZoneChanged(timeZone);
+            mNewLockScreenLargeClockViewController.onTimeZoneChanged(timeZone);
+        }
     }
 
-    void refreshFormat() {
+    void refreshFormat(String timeFormat) {
+        mTimeFormat = timeFormat;
         Patterns.update(mResources);
         mView.setFormat12Hour(Patterns.sClockView12);
         mView.setFormat24Hour(Patterns.sClockView24);
+        mView.onTimeFormatChanged(mTimeFormat);
+        if (mNewLockScreenClockViewController != null) {
+            mNewLockScreenClockViewController.refreshFormat();
+            mNewLockScreenLargeClockViewController.refreshFormat();
+        }
+    }
+
+    void refreshFormat() {
+        refreshFormat(mTimeFormat);
     }
 
     float getClockTextTopPadding() {
diff --git a/packages/SystemUI/src/com/android/keyguard/KeyguardStatusViewController.java b/packages/SystemUI/src/com/android/keyguard/KeyguardStatusViewController.java
index bc81a198c7e6b..826020c71159f 100644
--- a/packages/SystemUI/src/com/android/keyguard/KeyguardStatusViewController.java
+++ b/packages/SystemUI/src/com/android/keyguard/KeyguardStatusViewController.java
@@ -328,6 +328,11 @@ public class KeyguardStatusViewController extends ViewController<KeyguardStatusV
             mKeyguardClockSwitchController.updateTimeZone(timeZone);
         }
 
+        @Override
+        public void onTimeFormatChanged(String timeFormat) {
+            mKeyguardClockSwitchController.refreshFormat(timeFormat);
+        }
+
         @Override
         public void onKeyguardVisibilityChanged(boolean showing) {
             if (showing) {
diff --git a/packages/SystemUI/src/com/android/keyguard/KeyguardUpdateMonitor.java b/packages/SystemUI/src/com/android/keyguard/KeyguardUpdateMonitor.java
index 0fd8fd554c9c5..2071cfaf2bd90 100644
--- a/packages/SystemUI/src/com/android/keyguard/KeyguardUpdateMonitor.java
+++ b/packages/SystemUI/src/com/android/keyguard/KeyguardUpdateMonitor.java
@@ -182,6 +182,7 @@ public class KeyguardUpdateMonitor implements TrustManager.TrustListener, Dumpab
     private static final int MSG_USER_REMOVED = 341;
     private static final int MSG_KEYGUARD_GOING_AWAY = 342;
     private static final int MSG_LOCK_SCREEN_MODE = 343;
+    private static final int MSG_TIME_FORMAT_UPDATE = 344;
 
     public static final int LOCK_SCREEN_MODE_NORMAL = 0;
     public static final int LOCK_SCREEN_MODE_LAYOUT_1 = 1;
@@ -280,6 +281,7 @@ public class KeyguardUpdateMonitor implements TrustManager.TrustListener, Dumpab
             mCallbacks = Lists.newArrayList();
     private ContentObserver mDeviceProvisionedObserver;
     private ContentObserver mLockScreenModeObserver;
+    private ContentObserver mTimeFormatChangeObserver;
 
     private boolean mSwitchingUser;
 
@@ -1721,6 +1723,9 @@ public class KeyguardUpdateMonitor implements TrustManager.TrustListener, Dumpab
                     case MSG_LOCK_SCREEN_MODE:
                         handleLockScreenMode();
                         break;
+                    case MSG_TIME_FORMAT_UPDATE:
+                        handleTimeFormatUpdate((String) msg.obj);
+                        break;
                     default:
                         super.handleMessage(msg);
                         break;
@@ -1866,6 +1871,20 @@ public class KeyguardUpdateMonitor implements TrustManager.TrustListener, Dumpab
         mContext.getContentResolver().registerContentObserver(
                 Settings.Global.getUriFor(Settings.Global.SHOW_NEW_LOCKSCREEN),
                 false, mLockScreenModeObserver);
+
+        mTimeFormatChangeObserver = new ContentObserver(mHandler) {
+            @Override
+            public void onChange(boolean selfChange) {
+                mHandler.sendMessage(mHandler.obtainMessage(
+                        MSG_TIME_FORMAT_UPDATE,
+                        Settings.System.getString(
+                                mContext.getContentResolver(),
+                                Settings.System.TIME_12_24)));
+            }
+        };
+        mContext.getContentResolver().registerContentObserver(
+                Settings.System.getUriFor(Settings.System.TIME_12_24),
+                false, mTimeFormatChangeObserver, UserHandle.USER_ALL);
     }
 
     private void updateLockScreenMode() {
@@ -2449,6 +2468,22 @@ public class KeyguardUpdateMonitor implements TrustManager.TrustListener, Dumpab
         }
     }
 
+    /**
+     * Handle (@line #MSG_TIME_FORMAT_UPDATE}
+     *
+     * @param timeFormat "12" for 12-hour format, "24" for 24-hour format
+     */
+    private void handleTimeFormatUpdate(String timeFormat) {
+        Assert.isMainThread();
+        if (DEBUG) Log.d(TAG, "handleTimeFormatUpdate timeFormat=" + timeFormat);
+        for (int i = 0; i < mCallbacks.size(); i++) {
+            KeyguardUpdateMonitorCallback cb = mCallbacks.get(i).get();
+            if (cb != null) {
+                cb.onTimeFormatChanged(timeFormat);
+            }
+        }
+    }
+
     /**
      * Handle {@link #MSG_BATTERY_UPDATE}
      */
@@ -3059,6 +3094,10 @@ public class KeyguardUpdateMonitor implements TrustManager.TrustListener, Dumpab
             mContext.getContentResolver().unregisterContentObserver(mLockScreenModeObserver);
         }
 
+        if (mTimeFormatChangeObserver != null) {
+            mContext.getContentResolver().unregisterContentObserver(mTimeFormatChangeObserver);
+        }
+
         try {
             ActivityManager.getService().unregisterUserSwitchObserver(mUserSwitchObserver);
         } catch (RemoteException e) {
diff --git a/packages/SystemUI/src/com/android/keyguard/KeyguardUpdateMonitorCallback.java b/packages/SystemUI/src/com/android/keyguard/KeyguardUpdateMonitorCallback.java
index b722deab528ae..36617c2393529 100644
--- a/packages/SystemUI/src/com/android/keyguard/KeyguardUpdateMonitorCallback.java
+++ b/packages/SystemUI/src/com/android/keyguard/KeyguardUpdateMonitorCallback.java
@@ -57,6 +57,11 @@ public class KeyguardUpdateMonitorCallback {
      */
     public void onTimeZoneChanged(TimeZone timeZone) { }
 
+    /**
+     * Called when time format changes.
+     */
+    public void onTimeFormatChanged(String timeFormat) { }
+
     /**
      * Called when the carrier PLMN or SPN changes.
      */
diff --git a/packages/SystemUI/tests/src/com/android/keyguard/KeyguardClockSwitchControllerTest.java b/packages/SystemUI/tests/src/com/android/keyguard/KeyguardClockSwitchControllerTest.java
index 4559113bcf544..a2eaea1a37c51 100644
--- a/packages/SystemUI/tests/src/com/android/keyguard/KeyguardClockSwitchControllerTest.java
+++ b/packages/SystemUI/tests/src/com/android/keyguard/KeyguardClockSwitchControllerTest.java
@@ -23,6 +23,7 @@ import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
+import android.content.ContentResolver;
 import android.content.res.Resources;
 import android.test.suitebuilder.annotation.SmallTest;
 import android.testing.AndroidTestingRunner;
@@ -72,6 +73,8 @@ public class KeyguardClockSwitchControllerTest extends SysuiTestCase {
     Resources mResources;
     @Mock
     NotificationIconAreaController mNotificationIconAreaController;
+    @Mock
+    ContentResolver mContentResolver;
 
     private KeyguardClockSwitchController mController;
 
@@ -90,7 +93,8 @@ public class KeyguardClockSwitchControllerTest extends SysuiTestCase {
                 mColorExtractor,
                 mClockManager,
                 mKeyguardSliceViewController,
-                mNotificationIconAreaController);
+                mNotificationIconAreaController,
+                mContentResolver);
 
         when(mStatusBarStateController.getState()).thenReturn(StatusBarState.SHADE);
         when(mColorExtractor.getColors(anyInt())).thenReturn(mGradientColors);