In this case the case is significant and would cause it to break with your changes.
The issue is probably that it should have originally been 'Y-m-d h:n:s'
With your current settings it would be trying to set the date to: '2011-Jul-21 12:21:00', which would give a syntax error. See the meaning and case of the date settings on the page:
Try with the correct date string and let me know if you still get errors. If so, attach a current version of the page to your thread and I'll see if I can suggest a fix.