Sharing a read/write calendar between two people

Share iCloud calendars

If you set up iCloud on your Mac, you can use Calendar to manage your shared iCloud calendars.

If you also use iCloud Family Sharing, a Family calendar automatically appears in the iCloud calendar list. Everyone in your Family Sharing group can view and update the same Family calendar, so it’s a good way to keep track of events such as family camping trips and violin recitals.

Open Calendar for me

Share a calendar

1. Place the pointer over the calendar’s name in the calendar list, then click the Share Calendar button .If you don’t see the calendar list on the left, choose View > Show Calendar List.
2. Click Share With, then enter the names or email addresses of people you want to invite to share your calendar.If you don’t see Share With, click below the last name or email address in the Shared With list. If you see a Shared By [name] list instead of a Shared With list, only the person named can add people.
3. To keep someone from making changes to your shared calendar, Control-click the person’s name or email address in the Shared With list, then choose View Only.
4. To let anyone view your calendar—including people not listed in the Shared With list—select Public Calendar.To send people a link to subscribe to your public calendar, click the Share button , then choose how you want to send the link.People who subscribe to your public calendar can view it, but can’t change it. Only people listed in the Share With field who have view and edit privileges can make changes to the calendar.
5. Click Done.

People you added to the Shared With list are sent an invitation (a notification and an email) to join the shared calendar.

Here is another way that seem a little more streamlined. It's like subscribing to their feed.

Share calendar accounts

Share your calendar account with people who use the same CalDAV or Exchange calendar service (for example, with fellow employees at your company). You can choose whether others can edit the calendar account or only view it.

Open Calendar for me

Give another person access to your calendar account

1. Choose Calendar > Preferences, then click Accounts.
2. Select the calendar account.You can’t share individual calendars.
3. Click Delegation, click Edit, then click the Add button .
4. Enter the name of the person you want to give access to, then choose his or her name from the list that appears.
   • If you’re giving access to a CalDAV account, select the Allow Write checkbox to let the person edit your calendars.
   • If you’re giving access to an Exchange account, select the person’s level of access from the Calendars column.