diff --git a/src/com/android/settings/fuelgauge/BatteryChartView.java b/src/com/android/settings/fuelgauge/BatteryChartView.java
index f970072cb94..366946e12e2 100644
--- a/src/com/android/settings/fuelgauge/BatteryChartView.java
+++ b/src/com/android/settings/fuelgauge/BatteryChartView.java
@@ -103,8 +103,8 @@ public class BatteryChartView extends AppCompatImageView implements View.OnClick
             return;
         }
         // Sets the chart is clickable if there is at least one valid item in it.
-        for (int index = 0; index < mLevels.length; index++) {
-            if (mLevels[index] != 0) {
+        for (int index = 0; index < mLevels.length - 1; index++) {
+            if (mLevels[index] != 0 && mLevels[index + 1] != 0) {
                 setClickable(true);
                 break;
             }
@@ -155,6 +155,11 @@ public class BatteryChartView extends AppCompatImageView implements View.OnClick
             return;
         }
         final int trapezoidIndex = getTrapezoidIndex(mTouchUpEvent.getX());
+        // Ignores the click event if the level is zero.
+        if (trapezoidIndex == SELECTED_INDEX_INVALID
+                || (trapezoidIndex >= 0 && mLevels[trapezoidIndex] == 0)) {
+            return;
+        }
         // Selects all if users click the same trapezoid item two times.
         if (trapezoidIndex == mSelectedIndex) {
             setSelectedIndex(SELECTED_INDEX_ALL);
diff --git a/src/com/android/settings/fuelgauge/ConvertUtils.java b/src/com/android/settings/fuelgauge/ConvertUtils.java
index 2e8726e38ab..00dcb6be62b 100644
--- a/src/com/android/settings/fuelgauge/ConvertUtils.java
+++ b/src/com/android/settings/fuelgauge/ConvertUtils.java
@@ -70,8 +70,12 @@ public final class ConvertUtils {
     public static final int CONSUMER_TYPE_SYSTEM_BATTERY = 3;
 
     private static String sZoneId;
-    private static SimpleDateFormat sSimpleDateFormat;
-    private static SimpleDateFormat sSimpleDateFormatForHour;
+    private static String sZoneIdForHour;
+
+    @VisibleForTesting
+    static SimpleDateFormat sSimpleDateFormat;
+    @VisibleForTesting
+    static SimpleDateFormat sSimpleDateFormatForHour;
 
     private ConvertUtils() {}
 
@@ -140,25 +144,19 @@ public final class ConvertUtils {
             sZoneId = currentZoneId;
             sSimpleDateFormat =
                 new SimpleDateFormat("MMM dd,yyyy HH:mm:ss", Locale.ENGLISH);
-            sSimpleDateFormatForHour = null;
         }
         return sSimpleDateFormat.format(new Date(timestamp));
     }
 
     /** Converts UTC timestamp to local time hour data. */
-    public static int utcToLocalTimeHour(long timestamp) {
+    public static String utcToLocalTimeHour(long timestamp) {
         final String currentZoneId = TimeZone.getDefault().getID();
-        if (!currentZoneId.equals(sZoneId) || sSimpleDateFormatForHour == null) {
-            sZoneId = currentZoneId;
-            sSimpleDateFormat = null;
-            sSimpleDateFormatForHour = new SimpleDateFormat("HH", Locale.ENGLISH);
-        }
-        try {
-            return Integer.parseInt(
-                sSimpleDateFormatForHour.format(new Date(timestamp)));
-        } catch (NumberFormatException e) {
-            return Integer.MIN_VALUE;
+        if (!currentZoneId.equals(sZoneIdForHour) || sSimpleDateFormatForHour == null) {
+            sZoneIdForHour = currentZoneId;
+            sSimpleDateFormatForHour = new SimpleDateFormat("h aa", Locale.ENGLISH);
         }
+        return sSimpleDateFormatForHour.format(new Date(timestamp))
+            .toLowerCase(Locale.getDefault());
     }
 
     /** Gets indexed battery usage data for each corresponding time slot. */
diff --git a/tests/robotests/src/com/android/settings/fuelgauge/ConvertUtilsTest.java b/tests/robotests/src/com/android/settings/fuelgauge/ConvertUtilsTest.java
index e95b158391b..12913a29dc8 100644
--- a/tests/robotests/src/com/android/settings/fuelgauge/ConvertUtilsTest.java
+++ b/tests/robotests/src/com/android/settings/fuelgauge/ConvertUtilsTest.java
@@ -39,10 +39,12 @@ import org.mockito.MockitoAnnotations;
 import org.robolectric.RobolectricTestRunner;
 import org.robolectric.RuntimeEnvironment;
 
+import java.text.SimpleDateFormat;
 import java.util.Arrays;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.TimeZone;
 
@@ -254,6 +256,32 @@ public final class ConvertUtilsTest {
         assertBatteryDiffEntry(entryList.get(0), 68, 40L, 50L);
     }
 
+    @Test
+    public void testUtcToLocalTime_returnExpectedResult() {
+          final long timestamp = 1619196786769L;
+          ConvertUtils.sSimpleDateFormat = null;
+          // Invokes the method first to create the SimpleDateFormat.
+          ConvertUtils.utcToLocalTime(/*timestamp=*/ 0);
+          ConvertUtils.sSimpleDateFormat
+              .setTimeZone(TimeZone.getTimeZone("GMT"));
+
+          assertThat(ConvertUtils.utcToLocalTime(timestamp))
+              .isEqualTo("Apr 23,2021 16:53:06");
+    }
+
+    @Test
+    public void testUtcToLocalTmeHour_returnExpectedResult() {
+          final long timestamp = 1619196786769L;
+          ConvertUtils.sSimpleDateFormatForHour = null;
+          // Invokes the method first to create the SimpleDateFormat.
+          ConvertUtils.utcToLocalTimeHour(/*timestamp=*/ 0);
+          ConvertUtils.sSimpleDateFormatForHour
+              .setTimeZone(TimeZone.getTimeZone("GMT"));
+
+          assertThat(ConvertUtils.utcToLocalTimeHour(timestamp))
+              .isEqualTo("4 pm");
+    }
+
     private static BatteryHistEntry createBatteryHistEntry(
             String packageName, String appLabel, double consumePower,
             long uid, long foregroundUsageTimeInMs, long backgroundUsageTimeInMs) {