The date currently does not have its own CSS class. You'll need to do a little template modification.
6.7, Templates/public_ci_members.pl
Line 418 reads:
<a href="$ULTIMATEBB{"ubb=get_profile;u=$mbr"}">$data->{$mbr}->[0]</a><span class="ip-ci-numline"> - $tnum $date</span>Change it to read:
<a href="$ULTIMATEBB{"ubb=get_profile;u=$mbr"}">$data->{$mbr}->[0]</a><span class="ip-ci-numline"> - $tnum</span> <span class="ip-ci-dateline">$date</span>Then change the ip-ci-dateline class as you desire. Setting both ip-ci-numline and ip-ci-dateline to display: block will achieve the desired effect.
Do note that this is techincally a code hack. <img src="https://www.ubbcentral.com/boards/images/graemlins/wink.gif" alt="" />