I just learned how to create a public event from a private group:
How do I create an event for my group?
To create an event for your group, go to the group and click in the top right. Then select Create an Event from the dropdown menu. You need to be an admin to create an event in a large open group.
While creating your event, you’ll need to choose a privacy option. Note that once your group event is created, the privacy option can’t be changed.
I actually learned this the most backwards way possible. I created an event in a private group and didn’t notice that the question of privacy came up during the creation process. Later I wanted to know how to change the privacy settings and learned, through the info above, that I couldn’t.
Lesson learned. Next time I will pay better attention.
— Posted by Sandra Fernandez