Another attempt at fixing the `date_query` unit tests failures on PHP 5.2 and WordPress trunk.

See #5803 and https://travis-ci.org/buddypress/BuddyPress/jobs/32239701


git-svn-id: https://buddypress.svn.wordpress.org/trunk@8795 cdf35c40-ae34-48e0-9cc9-0c9da1808c22