I recently saw that same problem when I travelled outside of my home state of Colorado to Las Vegas, Nevada, switching from Mountain time to Pacific time. Rather to my horror, I opened up my iCal calendar to add a conference call a few days subsequent, just to see that everything had been automatically shifted to the local timezone, PST.

The problem is that if my call is at 9am Mountain time, do I want to add the conference call at 8am since that's the Pacific timezone schedule for that call? Or do I add it at 9am without paying attention, just to find that when I go home and change timezones again that it's now at 10am Mountain time?

Oy, it's a headache!

But we can fix it.

Here's the basic view of my iCal calendar when I was in the wrong timezone:

It doesn't indicate that it's switched timezones, but when I looked at it, I realized that my lunch with Karl was scheduled for 12.30pm, not 11:30am. What the heck? That's when I realized that there was a timezone problem.

To figure out how to solve it, I chose iCal --> Preferences and hopped to the "Advanced" tab:

As you can see, I selected "Turn on time zone support", but when I went back to iCal afterwards, nothing had changed.

In fact, I stared at iCal for a while before I noticed on the top right that it was now showing me the local time zone. So I clicked on it:

I chose my home time zone of Mountain time (MST), and suddenly, everything shifted an hour and my calendar on iCal was fixed:

(notice on the top right that it now says "Mountain Time", btw)

There's your answer. Now you know how to keep your iCal in your home time zone even as you travel. Hope that covers what you need!