With macOS Sierra, you can view a calendar that someone has published or shared by subscribing to it in Calendar. However, you can’t edit calendars you are subscribed to, such as the regional holidays calendar.
If you want to use a calendar that several people can edit, share it instead. To subscribe to a calendar from a link on the Internet or an email you received, click the link. If you do this, you can skip step 1 below, and the calendar’s web address is filled out for you in step 2. Otherwise:
- Choose File > New Calendar Subscription.
- Enter the calendar’s web address, then click Subscribe.
- Enter a name for the calendar in the Name field, then click the adjacent pop-up menu and choose a color.
- Click the Location pop-up menu, then choose an account for the subscription.
- If you choose your iCloud account, the calendar is available on all your computers and devices that are set up with iCloud. If you choose On My Mac, the calendar is saved on your computer.
- To get the calendar’s event attachments or alerts, deselect the appropriate Remove checkboxes.
- Click the Auto-refresh pop-up menu, then choose how often to update the calendar.
- To prevent alerts from appearing for this calendar, select “Ignore alerts.”
- Click OK.
- To make changes later, click the name of the calendar, then choose Edit > Get Info.
If you want to stop subscribing to someone else’s calendar, you can unsubscribe from it. Here's how.
- Control-click the calendar in the calendar list, then choose Unsubscribe.
- If you don’t see the calendar list on the left, choose View > Show Calendar List.
(This how-to is based on my experiences and info on Apple's support pages — where the images come from.)