To delete multiple events, I used the script in this answer - How to delete all events on many dates all at once but not the whole Calendar in Google Calendar?
var fromDate = new Date(2013,0,1,0,0,0);
var toDate = new Date(2013,0,4,0,0,0);
var calendarName = 'My Calendar';
// delete from Jan 1 to end of Jan 4, 2013
var calendar = CalendarApp.getCalendarsByName(calendarName)[0];
var events = calendar.getEvents(fromDate, toDate);
for(var i=0; i<events.length;i++){
var ev = events[i];
Logger.log(ev.getTitle()); // show event name in log
ev.deleteEvent();
}
However, the problem I have is that I have around 50 events per month which are recurring every year (birthdays), so it just goes on and on. How can I delete to make sure the recurring events are deleted as well?