In Calendar, click the "actions for" icon next to the calendar you'd like to share and select "Share/Permissions" from the dropdown menu. Decide if you want to invite people by email or share a link. To invite people via email type in a name or email address in the box. Then click "Viewer" and select the level of permissions you'd like to assign to the person you are sharing your address book with. You can also type a message if you'd like and click "Save". The person you shared your calendar with will receive an email with a link to view it.
To share a link, select "Anyone with the link and invited people" from the dropdown menu and click "Copy link" and share via email, text, instant message or any other way you communicate.
Tip: you can add an expiration date or a password by clicking the gear icon in the top right corner.