BuddyPress.org

As forums are provided totally by bbPress, it’s a possibility that as you can’t access the bbPress admin, you can’t set its time like you do with WordPress. Hmm.

EDIT: if you want to try a totally crazy “fix” which I have not even verified the problem exists, let alone the cause, try creating a new record in your wp_bb_meta table as follows:
object_type = bb_option
object_id = 0
meta_key = gmt_offset
meta_value = ? (set this to a number for the timezone offset, i.e. “1” for central european time)