Yes, this is very unfortunate but Google Calendar forces calendars that do not have a time zone specified to GMT (the correct behavior is to use local time, naturally).
The workaround is to download the ICS file to your phone/computer, and import it into Calendar. Amazingly, when you use this process, it uses local time as it should.
But it's quite a bit of trouble for you as you will have to delete the calendar and re-import each time your schedule changes.
Owner and Developer
MedRez.net Scheduling Tool