How to change the 9AM default for all-day Calendar events

calendar

Apple Calendar allows setting a default alert for events, including all-day events. But with all-day events there is no obvious way to control the time of the alert. Calendar preferences for alerts

All options displayed in the UI are for 9AM.
options for default alert time

This is mind-bogglingly restrictive. If I want to be alerted the day before an event, or two days before an event, I would never want to be alerted at 9AM—that's when I'm either sleeping or thinking about what I need to do that day.

How can I change this? Can I get more granular control somehow with defaults write? Or is there some other way? (A background process that detects new events added to my calendar and fixes their bad defaults?)

Best Answer

This question is for previous macOS version.

The time can be changed in macOS 10.14.3 Mojave:

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