A shared google calendar
Natalia and Alex both confirmed g calendars OK.
I have set one up, see here. The problem with public calendars is that while they are visible, not anyone can automatically add to them. So I am adding people manually upon request. Then syncing should not be a problem - but you do need to edit your own calendar events and assign them to the OpenCare PopUp Village Calendar.
Guys, most of you are added already.