To give newly created events a reminder automatically, set an alert in Calendar’s Alerts settings. Open Calendar, choose Calendar > Settings > Alerts, select the account you want to configure, then choose a time under Events. Calendar also has separate defaults for All Day Events and Birthdays. Apple describes these as defaults for new events; an event with its own alert setting may need to be adjusted individually. Apple’s Calendar Alerts guide

Set the default alert

  1. Open the Calendar app on your Mac.
  2. In the menu bar, choose Calendar > Settings, then click Alerts.
  3. Use the Account menu to select the calendar account whose events you want to affect.
  4. In the Events row, choose the alert time you want applied to new timed events. If you want reminders for all-day events too, choose a separate time in All Day Events.
  5. Leave the settings window. The selected default is now configured for that account’s new events.

Apple lists None as an available choice, which means no default alert. This setting chooses an alert timing, not a custom sound or a global notification style. You can also configure a separate default for birthdays in the Birthdays calendar. Apple’s Alerts settings guide

Choose between Mac-only and shared defaults

In the same Alerts pane, check Use these default alerts on only this computer if you want the setting to apply only on this Mac and not on other devices where you use Calendar. If you leave it unchecked, Apple says the defaults are not restricted to this computer. The result can depend on the account selected and how you use Calendar across devices, so confirm the correct account before changing the time.

This distinction is useful if you want a reminder on your Mac but prefer a different default elsewhere. If the option is unavailable or the change does not behave as expected for a particular calendar account, Apple’s documented controls do not promise identical behavior across every calendar service; choose the account deliberately and check a newly created event in that calendar.

Verify the setting on a new event

Create a small test event in the selected account and open its event details. Check that an alert appears at the intended time. For an all-day event, check the All Day Events default separately. This confirms what Calendar has applied to that event without assuming that changing the default rewrites every event already on your calendar.

Apple documents these as defaults for new events. Its separate alert troubleshooting guidance also tells users to choose a non-None time for Events or All Day Events when they need default alert times. Apple’s troubleshooting guide

Change an alert on one event

A default is a starting point, not a rule that fits every appointment. Open an individual event and edit its alert when it needs a different lead time or no reminder. Apple’s event-specific alert controls are documented separately from the default settings, and Exchange events support only one alert. Apple’s guide to setting an event alert

If an event’s details do not show the alert you expect, first confirm its calendar account and whether it is timed or all-day; those use separate defaults. Then choose a specific alert for that event if needed. Defaults are useful for routine events, while event-level settings handle exceptions such as a meeting that needs only a last-minute notification.

If the alert is set but no notification appears

A default alert time and macOS’s permission to display notifications are separate controls. If an event has an alert but no banner appears, check Apple menu > System Settings > Notifications > Calendar and make sure Allow notifications is on. Also check whether a Focus is active. Apple lists both notification settings and Focus as possible reasons alerts may not appear. Apple’s troubleshooting guide

Once the account, event type, and default timing are set, new events in that category can start with the reminder you chose. For anything that needs a different lead time, adjust the alert on the individual event.

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