Magic Mirror Birthday Updater

Year after year I have to update my birthday calendar on magic mirror. I use this solution:

https://forum.magicmirror.builders/topic/10126/getting-google-contacts-birthdays-into-calendar

But this year, some bugs made it impossible for me.

10:41:30 AM
Error
Exception: You have been creating or deleting too many calendars or calendar events in a short time. Please try again later.
Sync_Birth_Cal
@ 

I do nothing with this error, only ran the script again and again.

10:44:50 AM
Error
Exception: You have been creating or deleting too many calendars or calendar events in a short time. Please try again later.
Sync_Birth_Cal
@ 

This was more of a challenge. But one command added in last for loop fixed this problem.

  for (var t in eventToCopy){
    var newEvent = calendarDestination.createEvent(eventToCopy[t].getTitle(), eventToCopy[t].getStartTime(), eventToCopy[t].getEndTime());
  Utilities.sleep(500)
  }