Google-calendar – Is it possible to set a default alert for new events in Google Calendar

Very slow answer here, but you can always make your calendar private, which will prevent anyone from searching for and seeing your events.

You can also make your calendar public, but default to only show free/busy statuses.

When you select Make this calendar public, all of your events will appear in the public search results of Google Calendar and Google. Additionally, others will be able to view the calendar and its public events with your Calendar Address, or by adding the calendar to their 'Calendars' list.

Making your calendar public and selecting See only free/busy (hide details) means that your calendar information will not appear in the search results of any Google Calendar or Google search. Additionally, only your free/busy information will be visible to those who access your calendar at its address, or by adding it to their 'Calendars' list.

To keep your calendar private and only shared with the people you designate, be sure the 'Make this calendar public' option is not selected. For information on sharing your calendar with specific people, please visit this page.

It's a time zone conflict between your Google Calendar and the devices you sync it with. I had the same problem. One of my devices didn't have Daylight Savings set, and after syncing it would send a different time back to the Google servers.