Servers which miss that patch break because of various Auth schemes which require clocks to be reasonably in sync between machines.
So you get a bunch of outages whenever the next time shift is post-rules change.
I am less annoyed with DST than I am at how often we are fucking with it and breaking stuff.
(Did you know Australia has 11 possible time zones of which up to 9 are being used right now? It might even be 12. Most people don't, which is why most programmers fuck it up)
Yes, indeed. But we also have to change what people do manually when the rules change.
That's because every developer and sysadmin with more than a year of professional experience knows that you never, ever, do your own time zone math. You use your system time utils, and keep them updated so that your code reflects the latest laws.
Though, there are devs that work on those system tools. There are also cases where times need to sync and the changing can cause some issues. Stored times should be UTC but where they aren't it can makes some systems use local time incorrectly for a bit on the rollback. I have also seen network libs in games not use ticks for session starts that would be problematic on rollbacks playing at switchover. There have also been flaws in system time utils previously.
Lots of unnecessary potential edge cases, all for an unnecessary time change of time itself except a few places like Arizona.