[ticket/13118] Correctly use the provided datetime class

PHPBB3-13118
Merge pull request #3007 from nickvergessen/ticket/13118

[ticket/13118] Correctly use the provided datetime class

* nickvergessen/ticket/13118:
  [ticket/13118] Correctly use the provided datetime class
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/13118] Correctly use the provided datetime class