Use NTP? You Still Need Daylight Saving Time Patches
There seems to be a misconception out there that just because you run Network Time Protocol (NTP) on your network that you don’t need to patch your computers for the Daylight Saving Time nonsense that’s befallen North America. Fact is: even with NTP, you need those DST patches.
Time on an NTP server is communicated in terms of Greenwich Mean Time (GMT), otherwise referred to as Universal Time Coordinated (UTC). When your system synchronizes with an NTP server, it is obtaining time information relative to UTC. By convention, UTC is not subject to any Daylight Saving Time rules.
The local system is always responsible for converting UTC into the appropriate local time. All systems must be updated with new Daylight Saving Time rules anytime they change, even if NTP is being used else your clock may not properly reflect Daylight Saving Time.
Unix systems operate relative to UTC internally and use timezone information for displaying the date in various places. Windows PCs and Servers operate relative to local time. Some Windows programs, most notably Microsoft Outlook, also store important data in terms of local time, not GMT. That causes all kinds of trouble when DST rules change.
So if you haven’t patched your systems already, get cracking!