diff --git a/spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/JarWriter.java b/spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/JarWriter.java
index f2c365ac6e..aa51cfbb00 100644
--- a/spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/JarWriter.java
+++ b/spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/JarWriter.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2013 the original author or authors.
+ * Copyright 2012-2015 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -162,6 +162,7 @@ public class JarWriter {
 			throws IOException {
 		File file = library.getFile();
 		JarEntry entry = new JarEntry(destination + library.getName());
+		entry.setTime(getNestedLibraryTime(file));
 		if (library.isUnpackRequired()) {
 			entry.setComment("UNPACK:" + FileUtils.sha1Hash(file));
 		}
@@ -169,6 +170,28 @@ public class JarWriter {
 		writeEntry(entry, new InputStreamEntryWriter(new FileInputStream(file), true));
 	}
 
+	private long getNestedLibraryTime(File file) {
+		try {
+			JarFile jarFile = new JarFile(file);
+			try {
+				Enumeration<JarEntry> entries = jarFile.entries();
+				while (entries.hasMoreElements()) {
+					JarEntry entry = entries.nextElement();
+					if (!entry.isDirectory()) {
+						return entry.getTime();
+					}
+				}
+			}
+			finally {
+				jarFile.close();
+			}
+		}
+		catch (Exception ex) {
+			// Ignore and just use the source file timestamp
+		}
+		return file.lastModified();
+	}
+
 	/**
 	 * Write the required spring-boot-loader classes to the JAR.
 	 * @throws IOException
diff --git a/spring-boot-tools/spring-boot-loader-tools/src/test/java/org/springframework/boot/loader/tools/RepackagerTests.java b/spring-boot-tools/spring-boot-loader-tools/src/test/java/org/springframework/boot/loader/tools/RepackagerTests.java
index d7394d8c6e..019d74b8be 100644
--- a/spring-boot-tools/spring-boot-loader-tools/src/test/java/org/springframework/boot/loader/tools/RepackagerTests.java
+++ b/spring-boot-tools/spring-boot-loader-tools/src/test/java/org/springframework/boot/loader/tools/RepackagerTests.java
@@ -20,6 +20,7 @@ import java.io.File;
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.attribute.PosixFilePermission;
+import java.util.Calendar;
 import java.util.jar.Attributes;
 import java.util.jar.JarEntry;
 import java.util.jar.JarFile;
@@ -58,6 +59,17 @@ public class RepackagerTests {
 		}
 	};
 
+	private static final long JAN_1_1980;
+	private static final long JAN_1_1985;
+	static {
+		Calendar calendar = Calendar.getInstance();
+		calendar.set(1980, 0, 1, 0, 0, 0);
+		calendar.set(Calendar.MILLISECOND, 0);
+		JAN_1_1980 = calendar.getTime().getTime();
+		calendar.set(Calendar.YEAR, 1985);
+		JAN_1_1985 = calendar.getTime().getTime();
+	}
+
 	@Rule
 	public TemporaryFolder temporaryFolder = new TemporaryFolder();
 
@@ -275,7 +287,7 @@ public class RepackagerTests {
 	@Test
 	public void libraries() throws Exception {
 		TestJarFile libJar = new TestJarFile(this.temporaryFolder);
-		libJar.addClass("a/b/C.class", ClassWithoutMainMethod.class);
+		libJar.addClass("a/b/C.class", ClassWithoutMainMethod.class, JAN_1_1985);
 		final File libJarFile = libJar.getFile();
 		final File libJarFileToUnpack = libJar.getFile();
 		final File libNonJarFile = this.temporaryFolder.newFile();
@@ -284,6 +296,7 @@ public class RepackagerTests {
 		this.testJarFile.addFile("lib/" + libJarFileToUnpack.getName(),
 				libJarFileToUnpack);
 		File file = this.testJarFile.getFile();
+		libJarFile.setLastModified(JAN_1_1980);
 		Repackager repackager = new Repackager(file);
 		repackager.repackage(new Libraries() {
 			@Override
@@ -297,7 +310,9 @@ public class RepackagerTests {
 		assertThat(hasEntry(file, "lib/" + libJarFile.getName()), equalTo(true));
 		assertThat(hasEntry(file, "lib/" + libJarFileToUnpack.getName()), equalTo(true));
 		assertThat(hasEntry(file, "lib/" + libNonJarFile.getName()), equalTo(false));
-		JarEntry entry = getEntry(file, "lib/" + libJarFileToUnpack.getName());
+		JarEntry entry = getEntry(file, "lib/" + libJarFile.getName());
+		assertThat(entry.getTime(), equalTo(JAN_1_1985));
+		entry = getEntry(file, "lib/" + libJarFileToUnpack.getName());
 		assertThat(entry.getComment(), startsWith("UNPACK:"));
 		assertThat(entry.getComment().length(), equalTo(47));
 	}
diff --git a/spring-boot-tools/spring-boot-loader-tools/src/test/java/org/springframework/boot/loader/tools/TestJarFile.java b/spring-boot-tools/spring-boot-loader-tools/src/test/java/org/springframework/boot/loader/tools/TestJarFile.java
index a20671d726..00cdf10329 100644
--- a/spring-boot-tools/spring-boot-loader-tools/src/test/java/org/springframework/boot/loader/tools/TestJarFile.java
+++ b/spring-boot-tools/spring-boot-loader-tools/src/test/java/org/springframework/boot/loader/tools/TestJarFile.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2013 the original author or authors.
+ * Copyright 2012-2015 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -46,11 +46,19 @@ public class TestJarFile {
 	}
 
 	public void addClass(String filename, Class<?> classToCopy) throws IOException {
+		addClass(filename, classToCopy, null);
+	}
+
+	public void addClass(String filename, Class<?> classToCopy, Long time)
+			throws IOException {
 		File file = getFilePath(filename);
 		file.getParentFile().mkdirs();
 		InputStream inputStream = getClass().getResourceAsStream(
 				"/" + classToCopy.getName().replace(".", "/") + ".class");
 		copyToFile(inputStream, file);
+		if (time != null) {
+			file.setLastModified(time);
+		}
 	}
 
 	public void addFile(String filename, File fileToCopy) throws IOException {