more on time zones

converting to UTC from PDT or IST (date needs timezone short form)

$ TZ="UTC" date -d "Wed Apr 27 23:00:00 PDT 2011"
Thu Apr 28 06:00:00 UTC 2011

$ TZ="UTC" date -d "Wed Apr 27 23:00:00 IST 2011"
Wed Apr 27 17:30:00 UTC 2011

$ TZ="UTC" date -d "Wed Apr 27 11:00:00 IST 2011"
Wed Apr 27 05:30:00 UTC 2011

$ TZ="UTC" date -d "Wed Apr 27 11:00:00 PST 2011"
Wed Apr 27 19:00:00 UTC 2011

$ TZ="UTC" date -d "Wed Apr 27 11:00:00 PDT 2011"
Wed Apr 27 18:00:00 UTC 2011