diff --git a/staticlibs/framework/com/android/net/module/util/BestClock.java b/staticlibs/framework/com/android/net/module/util/BestClock.java
new file mode 100644
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+++ b/staticlibs/framework/com/android/net/module/util/BestClock.java
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+/*
+ * Copyright (C) 2021 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 com.android.net.module.util;
+
+import android.util.Log;
+
+import java.time.Clock;
+import java.time.DateTimeException;
+import java.time.Instant;
+import java.time.ZoneId;
+import java.util.Arrays;
+
+/**
+ * Single {@link Clock} that will return the best available time from a set of
+ * prioritized {@link Clock} instances.
+ * <p>
+ * For example, when {@link SystemClock#currentNetworkTimeClock()} isn't able to
+ * provide the time, this class could use {@link Clock#systemUTC()} instead.
+ *
+ * Note that this is re-implemented based on {@code android.os.BestClock} to be used inside
+ * the mainline module. And the class does NOT support serialization.
+ *
+ * @hide
+ */
+final public class BestClock extends Clock {
+    private static final String TAG = "BestClock";
+    private final ZoneId mZone;
+    private final Clock[] mClocks;
+
+    public BestClock(ZoneId zone, Clock... clocks) {
+        super();
+        this.mZone = zone;
+        this.mClocks = clocks;
+    }
+
+    @Override
+    public long millis() {
+        for (Clock clock : mClocks) {
+            try {
+                return clock.millis();
+            } catch (DateTimeException e) {
+                // Ignore and attempt the next clock
+                Log.w(TAG, e.toString());
+            }
+        }
+        throw new DateTimeException(
+                "No clocks in " + Arrays.toString(mClocks) + " were able to provide time");
+    }
+
+    @Override
+    public ZoneId getZone() {
+        return mZone;
+    }
+
+    @Override
+    public Clock withZone(ZoneId zone) {
+        return new BestClock(zone, mClocks);
+    }
+
+    @Override
+    public Instant instant() {
+        return Instant.ofEpochMilli(millis());
+    }
+}