diff --git a/oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/compaction/SegmentRevisionGC.java b/oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/compaction/SegmentRevisionGC.java
index 87307d1..4ed3661 100644
--- a/oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/compaction/SegmentRevisionGC.java
+++ b/oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/compaction/SegmentRevisionGC.java
@@ -115,16 +115,14 @@ public interface SegmentRevisionGC {
     void cancelRevisionGC();
 
     /**
-     * @return  timestamp of the last compaction or {@code null} if none.
+     * @return  time of the last compaction in milliseconds.
      */
-    @CheckForNull
-    String getLastCompaction();
+    long getLastCompaction();
 
     /**
-     * @return  timestamp of the last cleanup or {@code null} if none.
+     * @return  time of the last cleanup in milliseconds.
      */
-    @CheckForNull
-    String getLastCleanup();
+    long getLastCleanup();
 
     /**
      * @return  repository size after the last cleanup.
diff --git a/oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/compaction/SegmentRevisionGCMBean.java b/oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/compaction/SegmentRevisionGCMBean.java
index d21ccbd..09d563f 100644
--- a/oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/compaction/SegmentRevisionGCMBean.java
+++ b/oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/compaction/SegmentRevisionGCMBean.java
@@ -123,15 +123,13 @@ public class SegmentRevisionGCMBean
         fileStore.cancelGC();
     }
 
-    @CheckForNull
     @Override
-    public String getLastCompaction() {
+    public long getLastCompaction() {
         return fileStoreGCMonitor.getLastCompaction();
     }
 
-    @CheckForNull
     @Override
-    public String getLastCleanup() {
+    public long getLastCleanup() {
         return fileStoreGCMonitor.getLastCleanup();
     }
 
diff --git a/oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/file/FileStoreGCMonitor.java b/oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/file/FileStoreGCMonitor.java
index b66bea7..4ddc693 100644
--- a/oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/file/FileStoreGCMonitor.java
+++ b/oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/file/FileStoreGCMonitor.java
@@ -20,12 +20,10 @@
 package org.apache.jackrabbit.oak.segment.file;
 
 import static com.google.common.base.Preconditions.checkNotNull;
-import static java.text.DateFormat.getDateTimeInstance;
 import static org.slf4j.helpers.MessageFormatter.arrayFormat;
 
 import java.io.PrintWriter;
 import java.io.StringWriter;
-import java.util.Date;
 
 import javax.annotation.Nonnull;
 
@@ -93,12 +91,12 @@ public class FileStoreGCMonitor implements GCMonitor {
         this.status = status;
     }
 
-    public String getLastCompaction() {
-        return toString(lastCompaction);
+    public long getLastCompaction() {
+        return lastCompaction;
     }
 
-    public String getLastCleanup() {
-        return toString(lastCleanup);
+    public long getLastCleanup() {
+        return lastCleanup;
     }
 
     public long getLastRepositorySize() {
@@ -109,14 +107,6 @@ public class FileStoreGCMonitor implements GCMonitor {
         return lastReclaimedSize;
     }
 
-    private static String toString(long timestamp) {
-        if (timestamp != 0) {
-            return getDateTimeInstance().format(new Date(timestamp));
-        } else {
-            return null;
-        }
-    }
-
     public String getLastError() {
         return lastError;
     }