OFFICE 365 - OWA - SHARING A CALENDAR
In Outlook Web App you may share your calendar at a variety of levels.
1. Right-click on the desired calendar
2. Select Sharing Permissions to grant access
3. Enter the e-mail address of the other person
4. Select a level of detail
5. Click Send
Once rights are granted, you may right-click on Permissions below to manage shares and change permission levels.