If you use the OS X Calendar app, you can create a calendar event for a specific contact, or for a group.
In Contacts, select one or more contacts or groups.
Open Calendar, then drag the contacts or groups you selected in Contacts to a date in the Calendar window.
Make any adjustments to your event, then click Send.
To add more contacts to an existing event, double-click the event, then drag the contacts to the event.
For more information about Calendar, see Add, modify, or delete events.