Index: src/main/org/apache/tools/ant/taskdefs/Zip.java
===================================================================
--- src/main/org/apache/tools/ant/taskdefs/Zip.java	(revision 784603)
+++ src/main/org/apache/tools/ant/taskdefs/Zip.java	(working copy)
@@ -25,6 +25,8 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.text.DateFormat;
+import java.text.ParseException;
 import java.util.ArrayList;
 import java.util.Enumeration;
 import java.util.HashMap;
@@ -1525,6 +1527,31 @@
     }
 
     /**
+     * Last modification time for files stored in zip.
+     */
+    protected long lastModifed;
+    
+    /**
+     * Flag to indicate that last modifed has been set in the task.
+     * <p>
+     * Using a boolean is preferable to using -1 for the time since
+     * -1 is a valid time. 
+     */
+    protected boolean lastModifedSet;
+
+    /**
+     * Allows user to set the last modified time for content within the zip.
+     */
+    public void setLastModified(String dateString) {
+        try {
+            lastModifed = DateFormat.getInstance().parse(dateString).getTime();
+            lastModifedSet = true;
+        } catch (ParseException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    /**
      * Add a directory to the zip stream.
      * @param dir  the directort to add to the archive
      * @param zOut the stream to write to
@@ -1537,6 +1564,16 @@
     protected void zipDir(File dir, ZipOutputStream zOut, String vPath,
                           int mode, ZipExtraField[] extra)
         throws IOException {
+
+        if (lastModifedSet) {
+            // Use last modification time set in the task rather then the one from the file system.
+            dir = new File(dir.toURI()) {
+                public long lastModified() {
+                    return lastModifed;
+                }
+            };
+        }
+
         if (doFilesonly) {
             logOnFirstPass("skipping directory " + vPath
                            + " for file-only archive",
@@ -1594,6 +1631,12 @@
     protected void zipFile(InputStream in, ZipOutputStream zOut, String vPath,
                            long lastModified, File fromArchive, int mode)
         throws IOException {
+
+        if (lastModifedSet) {
+            // Use last modification time set in the task rather then the one from the file system.
+            lastModified = this.lastModifed;
+        }
+
         if (entries.contains(vPath)) {
 
             if (duplicate.equals("preserve")) {