While all internal users (i.e. Hampshire College Zimbra users) can view your free and busy time when trying to schedule an appointment with you, you must grant them the ability to look at your calendar more closely.
To access sharing options, right-click (or ctrl-click on a Mac) the calendar you want to share (it will be listed on the left hand pane in Zimbra), and select “Share Calendar.”
For internal (i.e. Hampshire College) users, there are three levels of sharing that you can choose to allow:
Viewer: Read-only access to your calendar
Manager: View, Edit, Add, Remove, Accept, Decline
Admin: View, Edit, Add, Remove, Accept, Decline, Administer (Administer includes deciding sharing privileges for the calendar, for instance.)
For external (non-Hampshire) selected users, you may allow viewing with a password that you provide.
For public, unrestricted viewing, you can supply a URL that will allow anyone to view the calendar.
If you share a calendar internally or externally (with the exception of public calendars), the user(s) you indicate will be sent an e-mail containing the URL to access the calendar, as well as the password if needed.