My time zone is EST, not Cupertino. Highly annoying. I had the same issue.
I have my time zone (in the Settings, General, Date & Time area) set to New York, but my calendar went to Cupertino with the last OS upgrade. To fix this, I did the following:
1. Go to SETTINGS
2. Scroll down to Mail, Contacts, Calendar (it's one item, not 3 separate items). Open it.
3. Scroll down to the Calendars section & select Time Zone Override. Open it & switch it to on. You should now see your default Time Zone, which mine is New York.
Your Calendar default should now be set to your new Time Zone.
4. Go to your calendar, pick an event & edit it.
5. Select the Start time & look at the Time Zone. Mine was still set to Cupertino.
6. Select the Time Zone.
7. In the entry box, type your new time zone. I typed New York.
After I saved the event, all of my other events, including recurring events, were now all set to New York, U.S.A. When I went back in & turned the Time zone override off, my calendar stayed as New York. When off, it's supposed to automatically default to your current location time zone. Why the OS upgrade changed everything to Cupertino is beyond me since I'm not located there & never had been.
There may be another way but this worked for me. I don't change time zones so I have no use for Cupertino.
I hope this helps.