DST observation is handled via system on the Mac - my guess is that those files haven't been updated to account for the change in Pakistan's DST rules. (No surprise, apparently the local government only decided not to observe DST 3 weeks ago.) These files should be updated with a future OSX update. It's technically possible to replace them with updated versions yourself, but you'd need to use Terminal and go into OS X's UNIX underpinnings to do so - if things go wrong you might need to do a re-install which isn't any fun at all, and even if they went right, I'm not sure what'd happen as soon as an Apple update tried to replace these files with updated versions.
So you probably have two workarounds until Apple issues an update that includes the correct DST data for Pakistan: You should either switch your location to somewhere like Usbekistan which currently has GMT+5, or you could turn off internet time sync and set the time zone manually.
Both of these aren't optimal, of course, but they shouldn't damage the system and could carry you over until an update to OS X fixes the issue.
Message was edited by: Baumi