You can set up appointments on your calendar that people can reserve. For instance, professors can have their students reserve time during office hours each week.
Click here for instructions on how to set up your calendar for reservations and how others can reserve those appointments.This feature is available only with a work or school Google Calendar account.
Click here for more Google Calendar Features:
Knowledge Base Article: Using Google Calendar to Set Up Appointment Slots
Schedule Meetings More Efficiently with Google Calendar
Adding College Calendars to Your Google Calendar
partially reposted from: https://support.google.com/calendar/answer/190998?hl=en