I believe this is resolved in v2.0.2. These were the changes if you would like to patch your instance:

In com/jivesoftware/base/UserTemplate.java, change lines 156 and 157 from this:

this.creationDate = (user.getCreationDate() != null) ? user.getCreationDate().getTime() : 0;
this.modificationDate = (user.getModificationDate() != null) ? user.getModificationDate().getTime() : 0;

To this:

this.creationDate = (user.getCreationDate() != null) ? user.getCreationDate().getTime() : -1;
this.modificationDate = (user.getModificationDate() != null) ? user.getModificationDate().getTime() : -1;

There is also a new test to add to line 90 of /com/jivesoftware/community/UserManagerTest.java:

@Test
 public void testCreateUserCreationDate() throws UserAlreadyExistsException {
       User userD = null;
       long before = System.currentTimeMillis();
       userD = manager.createUser(new UserTemplate("testCreateD", "createDPass", "testCreateD@localhost"));
       long after = System.currentTimeMillis();
       assert(before <= userD.getCreationDate().getTime() && after >= userD.getCreationDate().getTime());
}

Again, we recommend that you upgrade to 2.0.2 or higher in order to take advantage of the fix, but the changes to UserTemplate.java should also achieve what you're looking for.

Thanks,

Vinh