Link events (birthdays/anniversaries) from Google Contacts to Google Calendar in Android

In my contacts app, I have birthdays and anniversaries saved for most contacts. On most birthdays, I get a reminder 3 days before and then on the day of the birthday at 10 am. I have not created this setting but I'm good as long as I get a notification - so no complaints here. However, for some birthdays and all anniversaries, nothing like this happens. I get no notifications whatsoever. When I tap on a contact's anniversary, I am redirected to the calendar app where I can see an event for that contact's anniversary in the year that anniversary first occurred. However, for subsequent years, no such event is there. This same problem also happens for some birthdays. This is only happening in the Calendar app on Android. On opening the Google Calendar in a browser tab on my laptop, I can all birthdays and anniversaries populating properly. So my question is: What do I have to do so that such missing events are populated on Google Calendar so I can get a notification on my Android phone?