Change preferences in Calendar on Mac
Use Calendar preferences to change options for the accounts you use in Calendar and to customize the calendar view.
In the Calendar app on your Mac, choose Calendar > Preferences, then click a preference pane:
General: Change the view of your calendars, such as the number of days shown per week, the day your week starts on, birthdays, and holidays.
Accounts: Add, delete, turn on, and turn off your calendar accounts.
Alerts: Change default alert settings for events and birthdays, set an alert for when it’s time to leave for an event, and choose preferences for notifications.
Advanced: Choose settings such as time zone support and week number display, and clear the list of saved locations and attendees.
To learn about the options in a pane, click the Help button 
at the bottom of the pane.