You'll want to edit both Google Calendar and Salesforce to ensure the timezone settings are in sync.
Follow the instructions provided by Google at http://support.google.com/cale...
After that's completed, log in to Salesforce.
1. You'll need to update/check the timezone settings in two places. First, follow this path:
My Settings > Personal > Language and Time Zone (adjust time as needed)
2. Second, you'll want to check/edit the timezone following this path:
Setup > Administer > Company Profile > Company Information