We reviewed your instance. Here is the story!
The Time Zone you see when creating an event is based on the "Logged in" user. To view your time zone please follow the path:
Go to Your name (top right hand side) | My Settings |Personal | Language & Time Zone
Registrant, will see the Site Guest User time zone. Every Site has a Guest User with its own Time Zone
To view the time zone for the site guest users :
Go to Setup | Develop |Sites| Click on the respective site | Public Access Settings | View Users | Click on 'Site Guest User | see the Time Zone
I hope this helps.
Please let us know if we can be of more help.
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