[MNG-8478] Fix formatting of timestamp in logger

api/maven-api-core/src/main/java/org/apache/maven/api/MonotonicClock.java

@@ -19,6 +19,7 @@
 package org.apache.maven.api;
 
 import java.time.Clock;
+import java.time.Duration;
 import java.time.Instant;
 import java.time.ZoneId;
 import java.time.ZoneOffset;
@@ -77,6 +78,27 @@ public static Instant now() {
         return get().instant();
     }
 
+    /**
+     * Returns the initialization time of this monotonic clock.
+     * This is a convenience method equivalent to {@code get().start()}.
+     *
+     * @return the instant when this monotonic clock was initialized
+     * @see #startInstant()
+     */
+    public static Instant start() {
+        return get().startInstant();
+    }
+
+    /**
+     * Returns the elapsed time since clock initialization.
+     * This is a convenience method equivalent to {@code get().elapsedTime()}.
+     *
+     * @return the duration since clock initialization
+     */
+    public static Duration elapsed() {
+        return get().elapsedTime();
+    }
+
     /**
      * Returns a monotonically increasing instant.
      * <p>
@@ -93,6 +115,36 @@ public Instant instant() {
         return startInstant.plusNanos(elapsedNanos);
     }
 
+    /**
+     * Returns the wall clock time captured when this monotonic clock was initialized.
+     * <p>
+     * This instant serves as the base time from which all subsequent {@link #instant()}
+     * calls are calculated by adding the elapsed monotonic duration. This ensures
+     * consistency between the monotonic measurements and wall clock time.
+     *
+     * @return the initial wall clock instant when this clock was created
+     * @see #instant()
+     */
+    public Instant startInstant() {
+        return startInstant;
+    }
+
+    /**
+     * Returns the duration elapsed since this clock was initialized.
+     * <p>
+     * The returned duration is calculated using {@link System#nanoTime()}
+     * to ensure monotonic behavior. This duration represents the exact time
+     * span between clock initialization and the current instant.
+     *
+     * @return the duration since clock initialization
+     * @see #startInstant()
+     * @see #instant()
+     */
+    public Duration elapsedTime() {
+        long elapsedNanos = System.nanoTime() - startNanos;
+        return Duration.ofNanos(elapsedNanos);
+    }
+
     /**
      * Returns the zone ID of this clock, which is always UTC.
      *

impl/maven-logging/src/main/java/org/apache/maven/slf4j/MavenBaseLogger.java

@@ -19,9 +19,10 @@
 package org.apache.maven.slf4j;
 
 import java.io.PrintStream;
-import java.time.Clock;
-import java.time.Duration;
 import java.time.Instant;
+import java.time.ZoneId;
+import java.time.ZonedDateTime;
+import java.time.format.DateTimeFormatter;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -146,9 +147,6 @@
  */
 public class MavenBaseLogger extends LegacyAbstractLogger {
 
-    private static final Clock MONOTONIC_CLOCK = Clock.tick(Clock.systemUTC(), Duration.ofMillis(1));
-    private static final Instant START_TIME = MonotonicClock.now();
-
     protected static final int LOG_LEVEL_TRACE = LocationAwareLogger.TRACE_INT;
     protected static final int LOG_LEVEL_DEBUG = LocationAwareLogger.DEBUG_INT;
     protected static final int LOG_LEVEL_INFO = LocationAwareLogger.INFO_INT;
@@ -266,15 +264,6 @@ protected void writeThrowable(Throwable t, PrintStream targetStream) {
         }
     }
 
-    protected String getFormattedDate() {
-        Instant now = MonotonicClock.now();
-        String dateText;
-        synchronized (CONFIG_PARAMS.dateFormatter) {
-            dateText = CONFIG_PARAMS.dateFormatter.format(now);
-        }
-        return dateText;
-    }
-
     protected String computeShortName() {
         return name.substring(name.lastIndexOf(".") + 1);
     }
@@ -380,11 +369,15 @@ private void innerHandleNormalizedLoggingCall(
 
         // Append date-time if so configured
         if (CONFIG_PARAMS.showDateTime) {
-            if (CONFIG_PARAMS.dateFormatter != null) {
-                buf.append(getFormattedDate());
+            DateTimeFormatter formatter = CONFIG_PARAMS.dateFormatter;
+            Instant now = MonotonicClock.now();
+            if (formatter != null) {
+                ZonedDateTime zonedDateTime = now.atZone(ZoneId.systemDefault());
+                String dateText = formatter.format(zonedDateTime);
+                buf.append(dateText);
                 buf.append(SP);
             } else {
-                buf.append(Duration.between(START_TIME, MonotonicClock.now()).toMillis());
+                buf.append(MonotonicClock.elapsed().toMillis());
                 buf.append(SP);
             }
         }