Contacts birthdays customize reminder

Is there any way of adjusting the reminder generated in the contact birthdays calendar? Since the calendar is read only, my option is to enable or disable all reminders. I don’t need reminders for everyone I have a birthdate for and some I’d like a bit more notice. I can’t find any way to adjust either in the calendar settings or the contact itself and it seems a waste to have to recreate events for birthdays I want to remember.

AFAIK this is not possible right now.
Please see issues at GitHub and check for feature requests

FYI, this topic has been addressed here: