One method of quickly creating a lot of events in google calendar is to import a CSV file. However, there is no support for directly adding "recurring" events (birthdays, anniversaries, etc). Here's the workarond.

Summarized steps

1. create csv file with events (no recurring)
2. import csv into a new, temporary google calendar
3. export temporary google calendar to an ics file
4. edit ics file to change events into recurring
5. import ics file into a new, permanent google calendar.
6. delete temporary google calendar

Detailed steps

1. create csv file with events (no recurring)

The CSV format can be found at https://support.google.com/calendar/answer/37118?hl=en

2. import csv into a new, temporary google calendar

3. export temporary google calendar to an ics file

4. edit ics file to change events into recurring

4a. manually by adding RRULE:FREQ=YEARLY between each set of VEVENT begin/close statements. For example:

BEGIN:VEVENT
DTSTART;VALUE=DATE:20180520
DTEND;VALUE=DATE:20180521
RRULE:FREQ=YEARLY
...
END:VEVENT

or

4b. automatically by running this python

import icalendar
import os

def make_recurring():
    directory = os.path.dirname(__file__)
    with open(os.path.join(directory, 'noRecur.ics'), 'r') as fr:
        data = fr.read()

    cal = icalendar.Calendar.from_ical(data)
    for event in cal.subcomponents:
        if 'RRULE' not in event.keys():
            event.add('rrule', {'freq': ['YEARLY']})

    with open(os.path.join(directory, 'withRecur.ics'), 'wb') as fw:
        fw.write(cal.to_ical())

5. import ics file into a new, permanent google calendar.

6. delete temporary google calendar