I'm passing along a good answer from Neil@GCalToolkit.
The easiest way to do this is to go back to the very first occurrence of the event, change the date to the new start date for the series, and when prompted, select "This and following events". Please note that this can't be undone, and you'll lose any data in the deleted occurrences.
After trying everything, here is the answer. This is the only way I could find a way to have my personal google calendar show up on my business google suite / workplace calendar so all my employees could see that I was busy without needed to subscribe to a separate personal calendar (which I tried and everyone just checked my work calendar and scheduled ...
Updated answer Feb 2021. (for Google calendar on a desktop computer or laptop)
Go "My calendars" in the left panel
Hover over the calendar you want to update and click the three dots
Click "Settings and sharing"
Scroll down to "Event notifications"
Add the default notification type and duration
There you go!
Make sure to do it ...
In Google Calendar » Settings there is an option to add an additional timezone to event views. Check "Display secondary timezone" and choose the timezone you would like to have displayed for events. This is available through the desktop app settings, and should take effect for all events.
To clarify, this will not be displayed within the event ...