Simply put, you share your calendars and to do lists with others and you subscribe to others’ calendars and to do lists. When you share a calendar or list, you control who gets to see it and how they see it (view only or add and edit). When you subscribe to a calendar or list, the owner determines how you view it.
The following example shows the calendars you own and can share listed at the top of the Calendars area. Those you subscribe to are listed below the line.

Your calendars are viewed in the calendars and search panel accessed
through the small icon (
) near the top-right
of the calendar.

The to do lists that you subscribe to are mixed in with your own lists on the right side of the calendar page when viewed in its own window.

If you don’t see your to do lists, select Open in New Window from the Calendar’s Options menu.

Sharing
You can share with one person or many in the following ways:
Grant permission to specific friends to view only or to add and edit the calendar or list. Your friends see your calendar or list in their Yahoo! Calendar applications. With the add and edit permission, both you and your friend can keep the item up to date. See Sharing With Permissions.
Let friends without a Yahoo! ID see your calendar or list in their Web browser. See Sharing Through a Web Link.
Let friends using other calendar or list applications subscribe to your view-only calendar or list so that they can see it in their application. See Sharing Through a Subscription.
Let anyone who knows your Yahoo! ID see your view-only calendar or list. People type calendar.yahoo.com/yourID in their Web browser and they see what’s on your schedule. See Sharing With Anyone.
Note: You should only share with folks you really know, not with people you’ve barely met. Even with people you know, be thoughtful before providing them with access to your personal information, especially where you’ll be at specific dates and times. Even if you’ve shared a calendar or to do list, you can change your mind and hide the item from everyone or just a specific person. To learn more about our safety recommendations, click here.
Subscribing
Your friends and family can share their calendars and to do lists with you using the same approaches mentioned above. You can also subscribe to any calendar that uses the iCal format—a format that allows the exchange of calendar events across applications. Your subscription options:
Link to a calendar or list through an email from a friend who wants to share her information. See Subscribing Through an Email Message.
Type your friend’s Yahoo! ID in the subscription page. If he or she is sharing a calendar or to do list, we’ll find it for you. See Subscribing Using an Email Address.
Type any iCal address in the subscription page to add the calendar to your Yahoo! Calendar. This is a great way to track your favorite sports team’s schedule and your local art museum’s calendar. See Subscribing to Any Public iCal Calendar.
Through sharing and subscribing, you can keep up to date with all your friends and your special interests.