By default, you can schedule Appointments in 30 minute increments. Each User though can set their own Appointment time increments. For example, you could select 15 minute increment, you would be then able to schedule Appointment for 15 minutes, 30 minutes, 45 minutes, etc.
Appointment time increments are set on the User level, it is not an Organization wide setting.
- Click your Name in top right corner and select Calendar Preferences.
- Scroll down to Calendar Appearance Preferences section.
- Click Time Scale in Minutes dropdown and select appropriate increments.
- Click Save Preferences.