So I sat back and laughed as everyone struggled to get their PC's adjusted to the earlier onset of Daylight Saving Time. But I was apparently being a hypocrite, because I noticed my Linux machine's clock still on CST today! The problem turned out to be that the DST patch had been applied to the zoneinfo files, but never copied to the /etc/localtime file which is what the system uses to determine its own timezone. Simply copying the file fixed the problem (I didn't even have to reboot!) but still... one can't be too careful.