* to their desired timezone:
 * <pre>{@code
 * Instant now = MonotonicClock.now();
 * ZonedDateTime local = now.atZone(ZoneId.systemDefault());
 * }</pre>
 *
 * @see System#nanoTime()
 * @see Clock
 */
public class MonotonicClock extends Clock {
    private static final MonotonicClock CLOCK = new MonotonicClock();

    private final long startNanos;
    private final Instant startInstant;

    /**

    @Test
    @DisplayName("MonotonicClock singleton instance should always return the same instance")
    void testSingletonInstance() {
        MonotonicClock clock1 = MonotonicClock.get();
        MonotonicClock clock2 = MonotonicClock.get();

        assertSame(clock1, clock2, "Multiple calls to get() should return the same instance");
    }

    @Test
    @DisplayName("MonotonicClock should always use UTC timezone")

import javax.inject.Named;
import javax.inject.Singleton;

import java.time.Duration;
import java.time.Instant;
import java.util.HashSet;
import java.util.List;

import org.apache.maven.api.MonotonicClock;
import org.apache.maven.execution.BuildSuccess;
import org.apache.maven.execution.ExecutionEvent;
import org.apache.maven.execution.MavenSession;
import org.apache.maven.execution.ProjectExecutionEvent;

 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.maven.cling.transfer;

import java.time.Duration;
import java.time.Instant;

import org.apache.maven.api.MonotonicClock;
import org.eclipse.aether.transfer.AbstractTransferListener;
import org.eclipse.aether.transfer.TransferCancelledException;
import org.eclipse.aether.transfer.TransferEvent;

 * under the License.
 */
package org.apache.maven.cling.transfer;

import java.io.PrintWriter;
import java.time.Duration;
import java.util.concurrent.TimeUnit;

import org.apache.maven.api.MonotonicClock;
import org.apache.maven.api.services.MessageBuilder;
import org.apache.maven.api.services.MessageBuilderFactory;
import org.eclipse.aether.transfer.AbstractTransferListener;

import javax.inject.Named;
import javax.inject.Singleton;

import java.time.Duration;
import java.time.Instant;
import java.util.List;
import java.util.Set;

import org.apache.maven.api.MonotonicClock;
import org.apache.maven.artifact.Artifact;
import org.apache.maven.execution.BuildFailure;
import org.apache.maven.execution.ExecutionEvent;
import org.apache.maven.execution.MavenExecutionRequest;

import java.time.Instant;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.time.temporal.ChronoUnit;
import java.util.List;
import java.util.Objects;

import org.apache.maven.api.MonotonicClock;
import org.apache.maven.api.services.MessageBuilder;
import org.apache.maven.api.services.MessageBuilderFactory;
import org.apache.maven.execution.AbstractExecutionListener;
import org.apache.maven.execution.BuildFailure;

        protected void start() {
            if (start == null) {
                start = MonotonicClock.now();
                resumed = start;
            } else {
                resumed = MonotonicClock.now();
            }
        }

        protected void stop() {
            end = MonotonicClock.now();
            exec = exec.plus(Duration.between(resumed, end));
        }

        }
    }

    /**
     * Returns new builder from scratch.
     */
    static Builder newBuilder() {
        return new Builder().withStartTime(MonotonicClock.now());
    }

    class Builder {
        private Map<String, String> userProperties;
        private Map<String, String> systemProperties;
        private Instant startTime;

import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.Properties;

import org.apache.maven.api.MonotonicClock;
import org.apache.maven.artifact.repository.ArtifactRepository;
import org.apache.maven.eventspy.internal.EventSpyDispatcher;
import org.apache.maven.model.Profile;
import org.apache.maven.model.root.RootLocator;