Can I assign a custom alert time to a calendar entry?
If you go into the Calendar app you can setup a custom alert per entry. Here I've added an item to my Calendar and then double clicked on it to open up a dialog to customize. Under that menu is an alert section under the time/date area of the calendar entry, in that menu select customize. 

Calendar entry dialog



Alert menu



Customize menu



You can setup either an email or an audible sound for your specific time



CLI access to Calendar

You could use icalBuddy which was recommended in this other AD Q&amp;A titled: Displaying calendar events as text, in the terminal.

References


Set event alerts and receive notifications in Calendar on Mac