[ticket/12405] Valid timezone and dateformat for create_user() in tests

PHPBB3-12405
Merge pull request #2332 from VSEphpbb/ticket/12405

[ticket/12405] Valid timezone and dateformat for create_user() in tests

* VSEphpbb/ticket/12405:
  [ticket/12405] Valid timezone and dateformat for create_user() in tests
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12405] Valid timezone and dateformat for create_user() in tests