Wasim Baig thankfully posted a link to the updated tzdata file that includes the updates for Pakistan Standard Time (PKST). You can get it here:
If you’re using Ubuntu Linux, updating the system is a simple procedure, just extract the file for Asia and run zic:
wget ftp://elsie.nci.nih.gov/pub/tzdata2008c.tar.gz tar xzf tzdata2008c.tar.gz asia zic asia
That’ll update the timezone data and you can verify it by checking your system time/date. The timezone will show up as PKST instead of PKT.