Wikimedia Bugzilla is closed!

Some users have a null value for their user_registration in the user table. 

From enwiki: select user_id, user_name,user_registration from user where user_name='Jclemens';
+---------+-----------+-------------------+
| user_id | user_name | user_registration |
+---------+-----------+-------------------+
|  200029 | Jclemens  | NULL              | 
+---------+-----------+-------------------+

But the API reports the registration time as the current time when the query is run: the query

  http://en.wikipedia.org/w/api.php?action=query&list=allusers&aufrom=Jclemens&auprop=registration

returns: <u name="Jclemens" registration="2009-10-10T15:20:16Z" />

The problem is that the following line in APIQueryAllUsers.php is run regardless whether the user_registration is null, and apparently wfTimestamp defaults to the present time.

   $lastUserData['registration'] = wfTimestamp(TS_ISO_8601, $row->user_registration);