diff --git a/core/java/android/app/timedetector/ManualTimeSuggestion.java b/core/java/android/app/timedetector/ManualTimeSuggestion.java
index e7d619a..471606da 100644
--- a/core/java/android/app/timedetector/ManualTimeSuggestion.java
+++ b/core/java/android/app/timedetector/ManualTimeSuggestion.java
@@ -85,7 +85,8 @@
 
     @NonNull
     public List<String> getDebugInfo() {
-        return Collections.unmodifiableList(mDebugInfo);
+        return mDebugInfo == null
+                ? Collections.emptyList() : Collections.unmodifiableList(mDebugInfo);
     }
 
     /**
diff --git a/core/java/android/app/timedetector/PhoneTimeSuggestion.java b/core/java/android/app/timedetector/PhoneTimeSuggestion.java
index 233dbbc..dd02af7 100644
--- a/core/java/android/app/timedetector/PhoneTimeSuggestion.java
+++ b/core/java/android/app/timedetector/PhoneTimeSuggestion.java
@@ -23,7 +23,6 @@
 import android.util.TimestampedValue;
 
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 import java.util.Objects;
@@ -52,20 +51,25 @@
             };
 
     private final int mPhoneId;
-    @Nullable private TimestampedValue<Long> mUtcTime;
+    @Nullable private final TimestampedValue<Long> mUtcTime;
     @Nullable private ArrayList<String> mDebugInfo;
 
-    public PhoneTimeSuggestion(int phoneId) {
-        mPhoneId = phoneId;
+    private PhoneTimeSuggestion(Builder builder) {
+        mPhoneId = builder.mPhoneId;
+        mUtcTime = builder.mUtcTime;
+        mDebugInfo = builder.mDebugInfo != null ? new ArrayList<>(builder.mDebugInfo) : null;
     }
 
     private static PhoneTimeSuggestion createFromParcel(Parcel in) {
         int phoneId = in.readInt();
-        PhoneTimeSuggestion suggestion = new PhoneTimeSuggestion(phoneId);
-        suggestion.setUtcTime(in.readParcelable(null /* classLoader */));
+        PhoneTimeSuggestion suggestion = new PhoneTimeSuggestion.Builder(phoneId)
+                .setUtcTime(in.readParcelable(null /* classLoader */))
+                .build();
         @SuppressWarnings("unchecked")
         ArrayList<String> debugInfo = (ArrayList<String>) in.readArrayList(null /* classLoader */);
-        suggestion.mDebugInfo = debugInfo;
+        if (debugInfo != null) {
+            suggestion.addDebugInfo(debugInfo);
+        }
         return suggestion;
     }
 
@@ -85,10 +89,6 @@
         return mPhoneId;
     }
 
-    public void setUtcTime(@Nullable TimestampedValue<Long> utcTime) {
-        mUtcTime = utcTime;
-    }
-
     @Nullable
     public TimestampedValue<Long> getUtcTime() {
         return mUtcTime;
@@ -96,7 +96,8 @@
 
     @NonNull
     public List<String> getDebugInfo() {
-        return Collections.unmodifiableList(mDebugInfo);
+        return mDebugInfo == null
+                ? Collections.emptyList() : Collections.unmodifiableList(mDebugInfo);
     }
 
     /**
@@ -104,11 +105,23 @@
      * information is present in {@link #toString()} but is not considered for
      * {@link #equals(Object)} and {@link #hashCode()}.
      */
-    public void addDebugInfo(String... debugInfos) {
+    public void addDebugInfo(String debugInfo) {
         if (mDebugInfo == null) {
             mDebugInfo = new ArrayList<>();
         }
-        mDebugInfo.addAll(Arrays.asList(debugInfos));
+        mDebugInfo.add(debugInfo);
+    }
+
+    /**
+     * Associates information with the instance that can be useful for debugging / logging. The
+     * information is present in {@link #toString()} but is not considered for
+     * {@link #equals(Object)} and {@link #hashCode()}.
+     */
+    public void addDebugInfo(@NonNull List<String> debugInfo) {
+        if (mDebugInfo == null) {
+            mDebugInfo = new ArrayList<>(debugInfo.size());
+        }
+        mDebugInfo.addAll(debugInfo);
     }
 
     @Override
@@ -137,4 +150,39 @@
                 + ", mDebugInfo=" + mDebugInfo
                 + '}';
     }
+
+    /**
+     * Builds {@link PhoneTimeSuggestion} instances.
+     *
+     * @hide
+     */
+    public static class Builder {
+        private final int mPhoneId;
+        private TimestampedValue<Long> mUtcTime;
+        private List<String> mDebugInfo;
+
+        public Builder(int phoneId) {
+            mPhoneId = phoneId;
+        }
+
+        /** Returns the builder for call chaining. */
+        public Builder setUtcTime(TimestampedValue<Long> utcTime) {
+            mUtcTime = utcTime;
+            return this;
+        }
+
+        /** Returns the builder for call chaining. */
+        public Builder addDebugInfo(@NonNull String debugInfo) {
+            if (mDebugInfo == null) {
+                mDebugInfo = new ArrayList<>();
+            }
+            mDebugInfo.add(debugInfo);
+            return this;
+        }
+
+        /** Returns the {@link PhoneTimeSuggestion}. */
+        public PhoneTimeSuggestion build() {
+            return new PhoneTimeSuggestion(this);
+        }
+    }
 }
diff --git a/core/tests/coretests/src/android/app/timedetector/ManualTimeSuggestionTest.java b/core/tests/coretests/src/android/app/timedetector/ManualTimeSuggestionTest.java
new file mode 100644
index 0000000..de6f8f7
--- /dev/null
+++ b/core/tests/coretests/src/android/app/timedetector/ManualTimeSuggestionTest.java
@@ -0,0 +1,66 @@
+/*
+ * Copyright 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.app.timedetector;
+
+import static android.app.timezonedetector.ParcelableTestSupport.assertRoundTripParcelable;
+import static android.app.timezonedetector.ParcelableTestSupport.roundTripParcelable;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotEquals;
+
+import android.util.TimestampedValue;
+
+import org.junit.Test;
+
+public class ManualTimeSuggestionTest {
+
+    private static final TimestampedValue<Long> ARBITRARY_TIME =
+            new TimestampedValue<>(1111L, 2222L);
+
+    @Test
+    public void testEquals() {
+        ManualTimeSuggestion one = new ManualTimeSuggestion(ARBITRARY_TIME);
+        assertEquals(one, one);
+
+        ManualTimeSuggestion two = new ManualTimeSuggestion(ARBITRARY_TIME);
+        assertEquals(one, two);
+        assertEquals(two, one);
+
+        TimestampedValue<Long> differentTime = new TimestampedValue<>(
+                ARBITRARY_TIME.getReferenceTimeMillis() + 1,
+                ARBITRARY_TIME.getValue());
+        ManualTimeSuggestion three = new ManualTimeSuggestion(differentTime);
+        assertNotEquals(one, three);
+        assertNotEquals(three, one);
+
+        // DebugInfo must not be considered in equals().
+        one.addDebugInfo("Debug info 1");
+        two.addDebugInfo("Debug info 2");
+        assertEquals(one, two);
+    }
+
+    @Test
+    public void testParcelable() {
+        ManualTimeSuggestion suggestion = new ManualTimeSuggestion(ARBITRARY_TIME);
+        assertRoundTripParcelable(suggestion);
+
+        // DebugInfo should also be stored (but is not checked by equals()
+        suggestion.addDebugInfo("This is debug info");
+        ManualTimeSuggestion rtSuggestion = roundTripParcelable(suggestion);
+        assertEquals(suggestion.getDebugInfo(), rtSuggestion.getDebugInfo());
+    }
+}
diff --git a/core/tests/coretests/src/android/app/timedetector/PhoneTimeSuggestionTest.java b/core/tests/coretests/src/android/app/timedetector/PhoneTimeSuggestionTest.java
index c9a86dc..bee270e 100644
--- a/core/tests/coretests/src/android/app/timedetector/PhoneTimeSuggestionTest.java
+++ b/core/tests/coretests/src/android/app/timedetector/PhoneTimeSuggestionTest.java
@@ -16,11 +16,12 @@
 
 package android.app.timedetector;
 
+import static android.app.timezonedetector.ParcelableTestSupport.assertRoundTripParcelable;
+import static android.app.timezonedetector.ParcelableTestSupport.roundTripParcelable;
+
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotEquals;
 
-import android.os.Parcel;
-import android.os.Parcelable;
 import android.util.TimestampedValue;
 
 import org.junit.Test;
@@ -30,53 +31,67 @@
 
     @Test
     public void testEquals() {
-        PhoneTimeSuggestion one = new PhoneTimeSuggestion(PHONE_ID);
-        assertEquals(one, one);
+        PhoneTimeSuggestion.Builder builder1 = new PhoneTimeSuggestion.Builder(PHONE_ID);
+        {
+            PhoneTimeSuggestion one = builder1.build();
+            assertEquals(one, one);
+        }
 
-        PhoneTimeSuggestion two = new PhoneTimeSuggestion(PHONE_ID);
-        assertEquals(one, two);
-        assertEquals(two, one);
+        PhoneTimeSuggestion.Builder builder2 = new PhoneTimeSuggestion.Builder(PHONE_ID);
+        {
+            PhoneTimeSuggestion one = builder1.build();
+            PhoneTimeSuggestion two = builder2.build();
+            assertEquals(one, two);
+            assertEquals(two, one);
+        }
 
-        one.setUtcTime(new TimestampedValue<>(1111L, 2222L));
-        assertEquals(one, one);
+        builder1.setUtcTime(new TimestampedValue<>(1111L, 2222L));
+        {
+            PhoneTimeSuggestion one = builder1.build();
+            assertEquals(one, one);
+        }
 
-        two.setUtcTime(new TimestampedValue<>(1111L, 2222L));
-        assertEquals(one, two);
-        assertEquals(two, one);
+        builder2.setUtcTime(new TimestampedValue<>(1111L, 2222L));
+        {
+            PhoneTimeSuggestion one = builder1.build();
+            PhoneTimeSuggestion two = builder2.build();
+            assertEquals(one, two);
+            assertEquals(two, one);
+        }
 
-        PhoneTimeSuggestion three = new PhoneTimeSuggestion(PHONE_ID + 1);
-        three.setUtcTime(new TimestampedValue<>(1111L, 2222L));
-        assertNotEquals(one, three);
-        assertNotEquals(three, one);
+        PhoneTimeSuggestion.Builder builder3 = new PhoneTimeSuggestion.Builder(PHONE_ID + 1);
+        builder3.setUtcTime(new TimestampedValue<>(1111L, 2222L));
+        {
+            PhoneTimeSuggestion one = builder1.build();
+            PhoneTimeSuggestion three = builder3.build();
+            assertNotEquals(one, three);
+            assertNotEquals(three, one);
+        }
 
         // DebugInfo must not be considered in equals().
-        one.addDebugInfo("Debug info 1");
-        two.addDebugInfo("Debug info 2");
-        assertEquals(one, two);
+        builder1.addDebugInfo("Debug info 1");
+        builder2.addDebugInfo("Debug info 2");
+        {
+            PhoneTimeSuggestion one = builder1.build();
+            PhoneTimeSuggestion two = builder2.build();
+            assertEquals(one, two);
+        }
     }
 
     @Test
     public void testParcelable() {
-        PhoneTimeSuggestion one = new PhoneTimeSuggestion(PHONE_ID);
-        assertEquals(one, roundTripParcelable(one));
+        PhoneTimeSuggestion.Builder builder = new PhoneTimeSuggestion.Builder(PHONE_ID);
+        assertRoundTripParcelable(builder.build());
 
-        one.setUtcTime(new TimestampedValue<>(1111L, 2222L));
-        assertEquals(one, roundTripParcelable(one));
+        builder.setUtcTime(new TimestampedValue<>(1111L, 2222L));
+        assertRoundTripParcelable(builder.build());
 
         // DebugInfo should also be stored (but is not checked by equals()
-        one.addDebugInfo("This is debug info");
-        PhoneTimeSuggestion two = roundTripParcelable(one);
-        assertEquals(one.getDebugInfo(), two.getDebugInfo());
-    }
-
-    @SuppressWarnings("unchecked")
-    private static <T extends Parcelable> T roundTripParcelable(T one) {
-        Parcel parcel = Parcel.obtain();
-        parcel.writeTypedObject(one, 0);
-        parcel.setDataPosition(0);
-
-        T toReturn = (T) parcel.readTypedObject(PhoneTimeSuggestion.CREATOR);
-        parcel.recycle();
-        return toReturn;
+        {
+            PhoneTimeSuggestion suggestion1 = builder.build();
+            builder.addDebugInfo("This is debug info");
+            PhoneTimeSuggestion rtSuggestion1 = roundTripParcelable(suggestion1);
+            assertEquals(suggestion1.getDebugInfo(), rtSuggestion1.getDebugInfo());
+        }
     }
 }
diff --git a/services/core/java/com/android/server/timedetector/SimpleTimeDetectorStrategy.java b/services/core/java/com/android/server/timedetector/SimpleTimeDetectorStrategy.java
index 0b970bf..340fe3d 100644
--- a/services/core/java/com/android/server/timedetector/SimpleTimeDetectorStrategy.java
+++ b/services/core/java/com/android/server/timedetector/SimpleTimeDetectorStrategy.java
@@ -150,7 +150,8 @@
             if (!mCallback.isAutoTimeDetectionEnabled()) {
                 if (DBG) {
                     Slog.d(LOG_TAG, "Auto time detection is not enabled."
-                            + " time=" + time
+                            + " origin=" + origin
+                            + ", time=" + time
                             + ", cause=" + cause);
                 }
                 return;
@@ -159,7 +160,8 @@
             if (mCallback.isAutoTimeDetectionEnabled()) {
                 if (DBG) {
                     Slog.d(LOG_TAG, "Auto time detection is enabled."
-                            + " time=" + time
+                            + " origin=" + origin
+                            + ", time=" + time
                             + ", cause=" + cause);
                 }
                 return;
@@ -232,16 +234,16 @@
 
     @Override
     public synchronized void dump(@NonNull PrintWriter pw, @Nullable String[] args) {
-        pw.println("mLastPhoneSuggestion=" + mLastPhoneSuggestion);
-        pw.println("mLastAutoSystemClockTimeSet=" + mLastAutoSystemClockTimeSet);
-        pw.println("mLastAutoSystemClockTime=" + mLastAutoSystemClockTime);
-        pw.println("mLastAutoSystemClockTimeSendNetworkBroadcast="
+        IndentingPrintWriter ipw = new IndentingPrintWriter(pw, " ");
+        ipw.println("TimeDetectorStrategy:");
+        ipw.increaseIndent(); // level 1
+
+        ipw.println("mLastPhoneSuggestion=" + mLastPhoneSuggestion);
+        ipw.println("mLastAutoSystemClockTimeSet=" + mLastAutoSystemClockTimeSet);
+        ipw.println("mLastAutoSystemClockTime=" + mLastAutoSystemClockTime);
+        ipw.println("mLastAutoSystemClockTimeSendNetworkBroadcast="
                 + mLastAutoSystemClockTimeSendNetworkBroadcast);
 
-        IndentingPrintWriter ipw = new IndentingPrintWriter(pw, " ");
-
-        ipw.println("TimeDetectorStrategyImpl logs:");
-        ipw.increaseIndent(); // level 1
 
         ipw.println("Time change log:");
         ipw.increaseIndent(); // level 2
@@ -249,6 +251,7 @@
         ipw.decreaseIndent(); // level 2
 
         ipw.decreaseIndent(); // level 1
+        ipw.flush();
     }
 
     @GuardedBy("this")
diff --git a/services/core/java/com/android/server/timedetector/TimeDetectorStrategy.java b/services/core/java/com/android/server/timedetector/TimeDetectorStrategy.java
index 32cee2d..0a6c2e7 100644
--- a/services/core/java/com/android/server/timedetector/TimeDetectorStrategy.java
+++ b/services/core/java/com/android/server/timedetector/TimeDetectorStrategy.java
@@ -39,6 +39,12 @@
 
     /**
      * The interface used by the strategy to interact with the surrounding service.
+     *
+     * <p>Note: Because the system properties-derived value {@link #isAutoTimeDetectionEnabled()}
+     * can be modified independently and from different threads (and processes!). its use is prone
+     * to race conditions. That will be true until the responsibility for setting their values is
+     * moved to {@link TimeDetectorStrategy}. There are similar issues with
+     * {@link #systemClockMillis()} while any process can modify the system clock.
      */
     interface Callback {
 
diff --git a/services/tests/servicestests/src/com/android/server/timedetector/SimpleTimeDetectorStrategyTest.java b/services/tests/servicestests/src/com/android/server/timedetector/SimpleTimeDetectorStrategyTest.java
index 8a7edf7..7a0a28d 100644
--- a/services/tests/servicestests/src/com/android/server/timedetector/SimpleTimeDetectorStrategyTest.java
+++ b/services/tests/servicestests/src/com/android/server/timedetector/SimpleTimeDetectorStrategyTest.java
@@ -640,9 +640,9 @@
 
     private static PhoneTimeSuggestion createPhoneTimeSuggestion(int phoneId,
             TimestampedValue<Long> utcTime) {
-        PhoneTimeSuggestion timeSuggestion = new PhoneTimeSuggestion(phoneId);
-        timeSuggestion.setUtcTime(utcTime);
-        return timeSuggestion;
+        return new PhoneTimeSuggestion.Builder(phoneId)
+                .setUtcTime(utcTime)
+                .build();
     }
 
     private ManualTimeSuggestion createManualTimeSuggestion(long timeMillis) {
diff --git a/services/tests/servicestests/src/com/android/server/timedetector/TimeDetectorServiceTest.java b/services/tests/servicestests/src/com/android/server/timedetector/TimeDetectorServiceTest.java
index 9951e85..84b495f 100644
--- a/services/tests/servicestests/src/com/android/server/timedetector/TimeDetectorServiceTest.java
+++ b/services/tests/servicestests/src/com/android/server/timedetector/TimeDetectorServiceTest.java
@@ -140,10 +140,10 @@
 
     private static PhoneTimeSuggestion createPhoneTimeSuggestion() {
         int phoneId = 1234;
-        PhoneTimeSuggestion suggestion = new PhoneTimeSuggestion(phoneId);
         TimestampedValue<Long> timeValue = new TimestampedValue<>(100L, 1_000_000L);
-        suggestion.setUtcTime(timeValue);
-        return suggestion;
+        return new PhoneTimeSuggestion.Builder(phoneId)
+                .setUtcTime(timeValue)
+                .build();
     }
 
     private static ManualTimeSuggestion createManualTimeSuggestion() {