There are lots of calendars out there in the world wide web that you can subscribe to, many of which would support teaching and learning.
For example, if I visit this blog at Make Use Of, I find that there are many other Google Calendars that I can subscribe to. These include holidays that are specific to another culture, the calendars for professional sports teams, phases of the moon, television shows, Reddit AMA events and more!
You may also want to subscribe to internal calendars. These calendars are generally for things like rooms that can be booked (conference rooms for example). Here at division office, I have subscribed to the calendars for all the breakout rooms so that if I am setting up a meeting and need to find a space, my Google Calendar can factor that into my choices.
You can see that I have them all turned off (unchecked), but they are part of my resources available to me in my Google Calendar.