I went back and did some work on doing time-based color coding to make my recent referer viewer more useful. It now compares a last visited date to the referer date. Converting the latter to epoch time was surprisingly easy:
$date_parts = explode(":", $v[lastdate], 2);
$date = strtotime(str_replace('/', ' ', $date_parts[0]) . ' ' . $date_parts[1]);
I shaved off a few microseconds by adding an extra conditional so that this comparison only happens until the first time it hits an older date.
[update] Jesse wasn’t quite getting what I was talking about. I took a screenshot to show him, but thought hey, other people might be interested as well: