[BUGFIX] Object passed to date()

Function date() expects a timestamp as second parameter, not
an object.

Resolves: #52759
Releases: 6.2, 6.1, 6.0, 4.7, 4.5
Change-Id: I6821bafa51372c50d8903c63d62ea44933bc12b3
Reviewed-on: https://review.typo3.org/24712
Reviewed-by: Philipp Gampe
Tested-by: Philipp Gampe