Is it possible to batch change time on photos

Hi, I got a question regarding changing the time on photos. I just came back from Australia and have loads of photos from the trip as well as the photos from my friends. However, no one else set the time on the camera to the proper australia time. I got Denmark, German and American time zones. Is there anyway to change the time zone or something on the files so they are nicely in Order is that asking way to much, hope to hear form someone.

Nat