You can view your public calendars and events in your public calendar without logging in. To see your events in your public calendar your calendar and event must be public. To make a calendar public, click icon on My Calendars widget and open calendar settings. Here you can check desired calendars as public. When you create an event you need to make it public if you want to see it in Public Calendar. If your event belongs to a public calendar (checked as public above) it will be defined as public by default.
Public Calendar Page
You can reach your Public Calendar page in calendar settings.