fixup confusion between CDateToUnoTime and CDateToUnoDateTime

Change-Id: Ie3a13726086da113835f54f4eb1c68201edd44f9
Reviewed-on: https://gerrit.libreoffice.org/6582
Reviewed-by: Andras Timar <andras.timar@collabora.com>
Tested-by: Andras Timar <andras.timar@collabora.com>