Editing individual events on Google Calendar isn't difficult at all, but changing all of the events? That's not easy without some sort of program, such as this bulk edit calendar script.
Created by Derek Antrican, a senior mechanical engineering major, the script can rename all events on a select Google calendar, change their location or description, move the start times forward or back, change the duration of the events or delete them all in one go (be careful with that one, since it's not reversible).
This might come in handy if you want to move all of your regularly scheduled meetings up or back an hour or if you've switched to going to a different location for your haircuts/massages/shopping.
Use the keyword phrase filter to change only select events rather than all of them in your calendar. Here's the script:
Bulk Edit Calendar Events [Google Docs]